Sadly, Johnm has hit it on the head, they've discovered people will pay much more so they'll charge it! That's not just L/fee but gate price too.
It is a real shame as the FoS is an excellent event, I went to the first few in the mid-90's and it was good value, after a break of some years I went again '03-'05 as an engineer/camera op on the television OB so got in free but was shocked at the extent the prices had skyrocketed.
Like I say, it's a great pity as it's one of the only events of it's kind, well organised and suits the real enthusiast but is now so grossly over-priced it deters the people it was originally intended to attract.