But in this case it seems fairly clear cut - you pay "x" and you get to land your aeroplane. You have, in advance, all the information you need in order to decide whether you think it's worth it.
Are you sure?
Clearly you pay X to land your aircraft AND the "privilege" to fly into the show ground - other wise Goodwood would charge you the normal landing fee. (Has got me thinking whether the landing fee includes the entry fee or not this year - when I last went the entry fee was in addition to).
Once you have come out of the show ground you might or you might not decide you didnt get value for money for the extra privilege for which you paid.
As I said earlier personally I didnt think the event was worth the entry fee - but then clearly I am in a very small minority.