I bought my 6th grader (and wife) some pretty cool prepaid phones (Ampd Mobile – Hollywood), and each one tends to cost me about $10 a month, possibly as much as $15. It’s come in handy at times for staying on top of where he is, etc.
So the difference is I won’t get the unlimited calling and text option like some of the kids have. So he gets to flirt with having a luxury item, but it’s throttled back, and he pays for the time, so he tends to tell his friends not send Text messages about dumb things. (he gets an allowance and made a few hundred umpiring baseball games).