I'm assuming the cost of being at the stadium may have increased
I know it's easy to kick the stadium and sure, on some occasions it's valid - but they're not the source of all the world's ills (or the only cost involved in providing Weiner goodness).
Or even good old supply and demand.
If it's the only decent grub on offer and people want it, he will put his price up. Good on him if that's the case.