I've just been looking at Arsenal's ticket prices & arrangements.
Their season tickets include 4 European games, so cover 23 games rather than 19. They say they have to be used (attendance in person, transferred, or on their exchange) for 20 of those games. No requirement for minimum number of personal attendances.
They breakdown season tickets by category. They have 6 Cat A games, 12 Cat B and 5 Cat C, which they use to assign a price per seat, per category.
So their lowest-priced Adult ST is £1,073 and the Cat A games work out at £71.84 pro rats, the Cat B at £41.23 and the Cat C at £29.46. Im guessing these are the prices they'd refund you via the exchange.
But what absolutely astonished me was when I compared those numbers to their matchday prices. The equivalent full adult prices for each category are £74.30, £42.60 and £30.30. That's just coppers more than the pro-rata season ticket prices.
If an adult sold their ticket in 109 for the Villa game they'd get £43.84, but the ticket would go on sale for £73! That's 50% more than the pro-rata price.