DB.
I think one factor is that we seem prepared to pay higher prices so there is not much of a market pressure to keep them in check.
A few examples; aircraft hire charges and landing fees have increased way beyond inflation over the past seven years, probably because we don't shop around enough. Yes, input costs have gone up in the same period, but to nothing like the same extent.
The UK practice of paying landing fees when just landing to buy fuel particularly stands out. It is particularly hard on those whose aircraft have a short duration. As I have pointed out before the margin on AVGAS is very good indeed (unlike on retail petrol sales).
There are plenty of examples to show that a business model which allows more competitive pricing creates increased demand and healthy profits.
The UK also seems to suffer from an attitude of "Oh you fly, then you should be able to afford it" There have even been pilots on this forum suggesting that prices aren't too important because they (personally) have a fairly large disposable income. I understand that they don't have this attitude in the USA, and expect value for money in all things.
Rant over....