For me it is not so much the landing fee as the hassle factor involved. If you need to give 24 hrs PPR by semaphore, wear pink underpants and stand on your head before they will accept you, I can't be bothered.
If on the other hand if I can be flying along, decide I need a pee and a cuppa and simply land with no agro (a la USA), park in a nice area and enjoy a tea in a nice cafe then I don't mind paying £20 for the pleasure. Would be nice if that included over night parking for a number of nights too, especially at places like Bembridge.
That is why Bembridge was so good, you could just drop in as and when if you were passing and wanted a break.