Do you think the $100 + a Mac barrier has been a damper on the crowds of would be teenage app developers?
Just tell them you're 18, and don't care. Just don't flaunt it.
Or, found a company with the state ($30 in Georgia) and sign up for a corporate account.
Seriously, that $1000 entry fee is halved (or less, depending on the Mini spec you're looking at) to about the price of a netbook.
Or, you know, I've heard of people (cough) who run Hackintosh perfectly well and are developing apps without issue. Takes a bit of messing around a bit, but hey, kids usually have a bit of free time for this kinda thing.