Bioeconomics

The other day, I read that the average "price" paid by the "Tooth Fairy" currently hovers around $3,00.  This represents quite the increase over the $0.25 or so I used to receive.  More to the point, though, why do parents feel the need to reward children for tooth loss?  What's the incentive?  It's not as if children will go on some kind of strike if their parents don't pony up.  Some say it's not so much a payment as a small way to celebrate a developmental milestone, but if that's the case, shouldn't kids get like a thousand bucks for pubes?  And you just know that somewhere some kid has made the not-illogical assumption that if a tooth is worth three dollars, then a finger should bring in at least ten--and a leg below the knee could cover the cost of an Xbox.  Keep them away from the table saw.