As lucky9876coins pointed out, it doesn't necessarily take more bucks to play the mileage game. In fact, we usually end up flying much more, and in more comfort, for less total annual expenditure, than most other passengers.

Mileage Runners do very precise cost/benefit analysis, including figuring in their time (and the entertainment value of the trip). Personally I'd rather spend $300 flying to a town I've never been to, even if I don't really get to see the town, than spending the same $300 to buy tix to a football game, buy gas to drive to the stadium, pay for parking, etc., to sit outside in the cold for 4 hours. No one questions the logic or sanity of that activity, but people have a very hard time understanding what we do. (and that's good for us, because it cuts down on the competition for upgrades, cheap tix, etc).