What anyone paid for a ticket 50 years ago is irrelevant. Even if you adjust for inflation, consider this…production costs have grown exponentially over the decades. PA systems have become enormous, plus expanded lighting, effects, giant video, bigger crews, communication systems for that crew, then there are roadies/crew just for the acts themselves, with expertise concerning tech that didn't exist 25 years ago, all of which gets written into the ticket price.
The days of reasonably big bands that show up with just a 25 ft box truck containing all their gear(with three or four guys to handle it)and performing by just standing there (maybe hopping around a little)are pretty much over. People expect spectacle, and a flawless 'just like the record' experience. That's why so many you see on stage now aren't really playing. Then there are the pop acts with dancers/backup vocalists.
Add to that the operational and legal costs for the venues. The tragedy of The Who concert in Cincinnati,'79, changed everything. The Great White pyro disaster, even though in a small club, added to that further. Insurance premiums, tour underwriting, an increasingly heavy upgrade in security after 9/11(and in spite of that, the EODM incident occured, although in Paris)…all those sorts of things have become a significant portion of the ticket price, in spite of corporate sponsorship buy-ins. It ain't a groovy time at the Fillmore anymore.