Demographics play a major role, really. If you are in a state with tons of poor people (the South), it makes more sense to build 100k+ seats and sell the crappy ones for next to nothing. They will come to your stadium in droves, buy concessions, and buy merchandise when they aren't at the game. It helps grow your fanbase and is an investment that goes far beyond the return you get selling the seat for $11 seven times per year.