Good point.
I was looking back at my old City Hall ticket stubs from the 70s a while back. Saw Led Zeppelin, fourth row from the front, for 75P in 1972. That was about the same price as getting into the Fulwell end back then. (The ticket for Wembley in 73 was a pound).
When you consider the experience of going to a match back then with today's facilities ..today ..a seat, bogs not over flowing, ability to get a beer, not getting hit with sharpened pennies etc...the increase to, say, 35 quid a game isn't too bad.
Then consider how much you pay to see top groups these days in comparison (and few who could match Led Zeppelin in their prime). You don't get anywhere near the front and pay hundreds. It is worse than it was back in the day, but more than a hundred times more expensive.
So all in all, football is still a better deal.