I got this idea from Dave Ramsey. I've changed the numbers some, but the results are still pretty impressive.
Suppose that a 15 year old decides NOT to start smoking a pack of cigarettes a day and instead puts that money into a decent investment. Do you know how much he would have at retirement?
Take a deep breath - it's $1.6 MILLION.
That's not including any savings on life insurance or doctor bills or inflation (all of which are real and VERY likely). That's assuming a 10% rate of return.
The spreadsheet is available if you want it.