Indeed, most shows used to be free.
I don't think anyone objected to paying for the likes of Greenham Common or Mildenhall, but back then one got something for one's money. These days it's a very different matter. For example, I went to Waddington's show to see the Viggen and Vulcan and I was astonished to see how little there was to see. The static line-up was virtually nil, and this was supposed to be the RAF's "flagship" show of the year. The flying display was tame, and livened-up only by the Viggen. Even the Vulcan was a bit of a disappointment, performing somewhere closer to Metheringham than Waddington.
I've carped about this before, and the response is usually that I should accept that everybody loves these shows, as demonstrated by the attendance figures. It's spurious nonsense of course, as nobody has calculated how many people just don't go to shows any more because they're so poor.
I sympathise with the organisers for having to struggle with dwindling numbers of potential attendees and the ever-rising costs, plus absurd safety rules that make watching the show a better idea outside the airfield than in it. But my sympathy goes only so far. I see no attempt from anyone to make shows better, given the resources that remain. They seem to think that soldiering-on with the same old format is the way to go, even though it's gasping its last breath.