I'm not sure it's Everton who set the price for the travelling fans. My understanding is they sell the tickets to Sunderland at a reduced bulk price, that they are responsible for regardless of seats sold, Sunderland then sell that to their fans at a price that they expect to (a) make enough money to cover initial outlay, or (b) at a price where they can sell enough to fill the seats.
If they have seats remaining, within a block, they have not sold, they can return the allocation with enough notice for us to sell within our price bands.
If Sunderland saw fit to atempt to sell all their allocation at £20, then returned a section they still couldn't sell, should Everton be required to sell the returned tickets at £20 a seat? Effectively meaning that you are rewarding people who have turned up last minute over somebody who sits in the seat next to them in a seat they have sat in for years?
IT'S A POUND FFS!!!