The True Cost of an iPhone? Try $17,670

That's some phone!

OK, this is an exercise. The actual numbers will vary from customer to customer, based on cellular plan, age, tax bracket and retirement age.

But it tells a story.

If someone is already rich and has no worries about retirement, this may not matter.

But hardly anyone is.

Bob Glovsky, head of the financial planners' program at Boston University, points out that most Americans are saving far too little for their retirement, if anything at all. "Americans are a nation of consumers, not savers," he says.

Retirement is getting more expensive than ever. People are living a lot longer, and their medical costs are much higher. Meanwhile, our national savings rate has collapsed.

"The younger generation will be the only ones responsible for their own retirement," Glovsky says. "They can't expect anything from Mom and Dad because the boomers didn't even save enough for themselves."

In numbers? The Employee Benefit Research Institute says that among Americans between 25 and 34, less than half have saved more than $10,000. Less than one in three has $25,000.

For those between 35 and 44, the picture should be a lot better. It isn't.

Less than half have more than $25,000.

This isn't really about the iPhone. It's just about shopping ... and the true cost of the things we buy as long as we haven't saved enough for the things we will need.

Everyone understands how savings need time to grow. And most know that the average American is grossly undersaved for retirement.

But when the latest "must-have" consumer item comes along, hardly anyone seems to put two and two together. Instead, they rush out, waving their plastic.