You have a point there-the money doesn't really start to get spent as much until they are at least in mid to late elementary school, and the teens can also help out with classes to help make some money. But I know-my cousin was elite level soccer and it was over $30,000 a year-and then she randomly quit during our senior year. Cheerleading can be close to that if they are a squad that is competing nationally-between the multiple uniforms (football, basketball, and sometimes two competition uniforms, one for nationals), all the clothes that go with it (sweats, warmups, tees, lots of Soffe shorts, shoes, etc), competing (entry fees, travel/lodging/food), and other expenses.
Since we are on the topic of cost, TLC has a blog from the dad of Ava, one of the girls who competed in the first episode, and he talks about how they find every way they can in order to cut the costs. He makes all her dresses himself, they are not doing a ton of pageants (one state and one national a year), and so forth. I can only imagine what some of the families are doing now that the economy has gone south.