BOSTON (MainStreet) -- In a recent piece, we looked at five things people spend money on -- often a lot of money -- but never use.

Since that story appeared, we've heard from a number of readers who wanted to add to the list.

One commenter told of how the previous owner of his house shelled out thousands for an indoor sauna that was barely ever used once the novelty wore off. Others told of how swimming pools drained money like their liner leaked water. We also heard an inventory of just about every "as seen on TV" product you can think of.

It is not that the quality or value of such purchases is lacking, so much as the fact that household budgets are squandered on something that proves an impulse buy or fad.

If you really do love your new chicken rotisserie and use it all the time, good for you -- it was a wise purchase. But too often we all ring the register with items that seemed like a good idea at the time but quickly gather dust in the basement.

We took a look at five other items, some less tangible than our previous list, that people often buy and never make full use of.

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Buying mobile apps, whether via Apple's (Stock Quote: AAPL) walled garden or the broader population facilitated by Google (Stock Quote: GOOG) for the Android OS, can become addictive quickly.

Browsing the iOS app store, for example, is always a quick way to end up spending money and -- 99 cents here, $2.99 there -- the charges accumulate rapidly. A low price point makes such purchases an easy, one-click impulse buy, which is exactly what Apple wants from iPhone and iPad users. Limited-time-only deals of 50% off are all it takes to go on a digital shopping spree for utilities and games.

In no time at all, the meager flash memory fills up with screen after screen of real estate hogging icons.

The cost of all these downloads wouldn't really be all that problematic -- if we actually used what we paid for.

According to Localyctics, a Boston software company specializing in app analytics, as many as 26% of users will try out an app and abandon it after just one use.

While true that 74% of new customers will use an app more than once, the large number of ignored apps could eventually lead to changes in how they are priced. User engagement and loyalty is key for an app pulling its weight, especially for those that rely on advertising or in-app purchases. Lacking reliable usage could lead many free apps to start charging as they seek revenue.

Research by Pinch Media, which provides tools for mobile application developers, found similar findings. With free applications, an average 20% of users last year revisited an app the day after they download it; after 30 days, less than 5% are still using it. Paid apps do better securing user retention over time, but free apps garner about 6.6% more usage.

Given the amount of money spent on apps each year -- $50 on average per person, according to the Online Publishers Association -- and the fact that as many as 54 million people are expected to use apps this year, that's a whole lot of spending money laying idle behind our collective touchscreens.

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Magazines subscriptions
Magazines subscriptions are like potato chips -- it is hard, if not impossible, to stop at just one.

It starts with a subscription to the New Yorker or Martha Stewart Living. Then, with your name flagged in a database, offers start coming fast and furious: "12 issues for $12," "67% off cover price," "subscribe now for a free gift." Almost immediately after subscribing, renewal notices will start arriving with increasingly urgent pleas to get you to re-up lest your mailbox go empty. If you subscribe online, and are not careful, the "auto renew" box will be a gift that keeps on giving.

It is not that subscriptions are a bad thing. But many of us give into the urge to keep subscribing to new publications -- taking advantage of those great special offers -- even with little time to keep up with all that reading.

It isn't uncommon in many households for there to be a stack of old New Yorkers waiting to be caught up on in a marathon session of page flipping, and many a kitchen is cluttered with barely cracked issues of Cooks Illustrated, Woman's Day or Bon Appetit.

The rise of e-Readers, smartphones and tablets gives even more ways to subscribe and perpetuate the cycle. According to the Association of Magazine Media's 2011 Factbook, 51% of consumers between 18 and 34 are reading magazines electronically, with 41% of them paying for that content. Among current magazine subscribers, 53% choose to renew with a digital product.

Don't think those electronic subscriptions will automatically reduce the nation's living room clutter. According to MPA, 87% of magazine readers on digital devices still also want a printed copy, with 75% agreeing that digital content is a complement, rather than a print replacement.

Going digital isn't going to necessarily save you much money -- or ensure you read what you pay for. The current pricing models for electronic content are all over the map, with, for example, iPad-only versions often costing more than print and even more than a print subscription that includes a digital version. (The reason, in many cases, is to make up for the impact on advertisers.)

Digital editions are becoming more and more popular. Hearst says that in September it had more than 300,000 paid users for its digital editions sold through iTunes, the Barnes & Noble (Stock Quote: BKS) Nook and the online Zinio format, representing a 10-fold increase from a year earlier.

For consumers, the ease of digital subscriptions, paired with the abundance of media consumed on devices, likely means less time spent getting your full money's worth out of every edition. At the very least, younger Americans are increasingly letting computers and games cut into their reading time.

According to the most recent data from the U.S. Bureau of Labor Statistics, last year people 75 and older averaged 1.1 hours of reading per weekend day and 18 minutes playing games or using a computer for leisure. But people ages 15 to 19 read for an average of six minutes per weekend day while spending 1.1 hours playing games or using a computer.

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"Parking" on online addresses
Over the years, many speculators have turned to online "real estate."

The game was once fairly easy. Find a domain name you think might have value and register it. Then, when a deep-pocketed entity decides your URL has the name they need, wait for them to shell out big bucks.

This year alone, sold for $2.6 million, netted $1 million and (meaning "stocks" in German) pulled in $700,00, the same amount paid for was a relative bargain at $500,000.

Also gobbling up domain names in .com, .net., .tv, .xxx and other flavors are average folks, who want a personalized domain name to go with their blog, photo pages and business ventures.

Human nature being what it is, many domain names are merely "parked," unused except for the random ads their registration company uses to fill the empty space. There are names that have potential value that remain parked for years awaiting a big buyer to come along, among them,,,, and

For the average would-be Web publisher, it's unlikely their handful of registrations are going to be a budget buster. But, with registration companies such as GoDaddy charging between $11 to $17 a year for many domain names, the cost can add up year after year if you merely buy and renew without actually bothering to add content.

Internet-wide, that's a huge amount of money being left on the table. According to the service DomainTools, which offers site name research and services, as of Tuesday there were nearly 134 million active Web sites but more than 407 million that have been deleted or expired. For the 24-hour period on that date alone, 73,377 sites expired.

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Automobile extras
America has a love affair with cars, and many lust after all the cutting-edge bells and whistles a new vehicle can accommodate.

But even though add-ons and extras may make your new car the envy of the block, many are likely overkill.

Take the 2012 line of Ford (Stock Quote: F) Mustangs for example, a stylish car getting great reviews. The price swing model to model, though, is big.

The baseline V-6 model starts at a reasonable $22,310. But start adding in extras, a better engine and various aesthetic touches and that off-the-lot model could turn into a top-of-the-line Shelby GT500 convertible that will cost nearly $54,000. That's not to say it is not a great car, but how many of us would really have the need for a 5.4 liter supercharged V8 engine under the hood? The zero -to-60 rankings rarely come into play when fighting rush-hour traffic or taking the kids to soccer practice.

The difference between muscle cars is just an extreme example. Car buyers routinely pay for extras (often under pressure from a clever sales rep) they probably don't need and could live happily without -- fabric protection, rustproofing, vehicle identification number etching, trim, moonroofs/sunroofs, GPS systems, iPod jacks and on-dash LCD screens among them.

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Extended warranties
Extended warranties, according to consumer advocates, are usually not worth even a fraction of what people pay for them.

It isn't just car dealerships using high-pressure tactics to up their bottom line by selling extended plans. Retailers such as Radio Shack (Stock Quote: RSH), Best Buy (Stock Quote: BBY), Wal-Mart (Stock Quote: WMT) and OfficeMax (Stock Quote: OMX) have made pushing these plans a job requirement for sales staff and cashiers.

Setting aside the issues of whether these plans are a rip-off, what they cover and what they won't make good on, consumers need to start by asking: "Do I even need this?"

Many manufacturers -- in particular carmakers -- have started offering longer and better warranty periods with their products as an incentive to buyers. By the time this coverage lapses, any repair needs are less and less likely to fall within the agreement with a third-party warranty provider. The policy may also be an unnecessary cost if, in the case of a car, you are likely to not keep it for much longer than the number of years included under the original warranty.

Adding evidence that in most instances an extended warranty will never be used comes from a recent study conducted by Consumer Reports.

It found that "appliances usually don't break during the extended-warranty period" and do so "normally after the standard warranty has expired but within two to three years of purchase."

"Even when breakdowns do occur in that time, the median cost of repair, $150, isn't much more than the median price of a warranty, $142," they wrote. "And if the product doesn't break, you haven't wasted your money on needless protection."

You might do well to also check in with your credit card issuer before buying a computer, appliance or piece of electronics. American Express (Stock Quote: AXP), for instance, automatically extends the warranty of purchases made with some of its cards.

For more examples of the everyday things we buy and never end up using, check out the original story in the series, 5 Things We Buy, Then Never Use!