A friend and I did about 30k in profit at age 15 in '02-'03, and it would have been way higher if we weren't having issues with merchant accounts. I doubt it would have gone into the millions, but easily 100k-200k.

Finding a market and executing on an opportunity isn't that difficult of a thing to do - the trick is finding one within your grasp. This was virtual goods, so it required almost no upfront capital and very little development and maintenance costs. It's no massively-scalable startup, but when your goal is just to create a profitable lifestyle business, it isn't actually that complicated.