That's the thing though, the FA have no idea what the best price to charge for the game is, why are they trying to pretend they do?
The FA used to get disputes every round when prices had to be agreed. There was a big one for City v S****horpe in 2006.
City wanted to charge £15, scunny wanted £20+. It took ages to get sorted and ended up being £18, but city charged £15 and susidised the home fans. After more of these they just decided to set a minimum price and let the home team decide.
I believe it was Bernstien who put it up to £15, but reduced it as a concession for the FA Cup final being in the evening.