NEW YORK (MainStreet) -- Why do otherwise sensible U.S. adults choose an ancient pagan-based holiday to go into full-blown financial zombie mode and spend good money on bad-for-you candy, goofy costumes and cardboard decorations they wouldn't look at twice any other time of the year?

One answer - it's fun. That's what consumers and financial experts told MainStreet when asked why so many Americans are increasingly seeing Halloween as a big-time national holiday and thus deserving of all the spending, partying and candy-eating.

The average consumer will shell out $74.34 Halloween spending in 2015, down slightly from $77.52 last year, according to the National Retail Federation. Some 17% of adults surveyed by the NRF said they'd curb their Halloween spending over economic concerns, and though down about $500 million, Halloween spending is still at a spirited $6.9 billion in total. 

Bill Fish, founder and president of Cincinnati-based ReputationManagement.com, acknowledges his wife and he are "out of the ordinary" when they spend up to $4,000 annually on Halloween, but there's a reason for that.

"It's my wife's favorite holiday by a dramatic margin," Fish says. "It seems as if half our basement stores creepy things that come out for the month of October. Halloween is just a great adult holiday."

Fish has an adult-only party each year on the Saturday before Halloween, where everyone has to be in costume. "We have a band, plenty of food and drinks, and we've begun to notice that looking like a fool in a costume helps people be less up tight, and a good time is had by all," he says. "This year, we have 150 people on the invite list and have had our costumes picked out for six months."

That's some heavy-duty Halloween hi-inks, right there, even if it is an extreme version of what most consumers will spend on the holiday.

Take costumes. According to Coupon Cabin, 90% of American adults will spend between $20 and $150 on Halloween costumes. But like Fish and his family, you don't have to stop there - not when you can spend $917 on a vintage Elvis Presley costume or $1,427 on an adult panda mascot costume.

Then there's the allure of spirits during the Halloween season - and not the kind that float around the cemetery spooking passers-by.

Alcohol will join costumes in propping up Halloween spending this year. According to a survey of 15,000 California adults for BevMo, one of the largest beverage retailers in the Golden State, 44% of respondents said they would be spending in excess of $100 for alcohol for Halloween, while a similar percentage said they would spend between $50 and $100. With Halloween on a Saturday night this year, brews and booze may take on an even more prominent role in celebrating the holiday among U.S. adults.

Again, most U.S. consumers won't go that far this Halloween, but they will be shelling out some significant cash on the horror-filled holiday. "It seems that the national Halloween spending forecast is down this year from last, but I personally am creating a costume, buying treats and having a Halloween baby shower this year," says Pamela Layton McMurtry, a Halloween pop culture expert located in Kaysville, Utah. "I'm thinking about spending $100 for my husband and my household."

Of course, there's the decorative aspect. Lyra Marble, owner of Los Angeles-based Mr. Bones pumpkin patch for the past 30 years, says consumer spending on pumpkins has risen 15% to 25% annually in recent years, with a huge spike in activity before Halloween. "Even through the recession, pumpkin sales remained steady, as you have to buy a new one each holiday," Marble says. "We've seen Halloween only grow and grow in popularity."

Of course, not everyone is donning a Dracula costume and going all out this Halloween season. "We'll spend about $10 - tops - for kids coming to the door this Halloween," notes Henry Stimpson, a Wayland, Mass. public relation's executive.

To cut costs, expect consumers to turn to digitally-based bargain Halloween sites, like VarageSale.com, which allows you to sell last year's Batman costume to someone else, and buy a used warlock costume, or any costume, at a big discount.

That might be a scary though for holiday revelers, but Stimpson's way is easier on the wallet, albeit in a "bah-Halloween humbug" sort of way.

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