I know that people are pissed off, but you have to realize that U2 is one of the most popular bands in the world. They, the Rolling Stones and maybe one or two other acts can charge whatever they want because of the broad appeal they have around the world. GA tickets and upper bowl tickets are reasonably priced, frankly they could charge more for those as well and people would pay.
We live in a world where the prices for almost everything is going up, expecting a concert from one of the biggest bands in the world to not go up is just unrealistic. In a world where album sales are stagnant, bands now need to make their money in concert tours. Also, I wouldn't expect altruistic socialism from a semi-conservative Catholic band whereas Eddie Vedder is more liberal than most, I mean he supported Ralph Nader and the Green Party. U2 is a capitalist business and they want to make money. Anyways, just saying that politics and world view enters into it a bit.
Anyways, I still agree it sucks, but I can see why they're doing it.