According to this, Bristol City earned £700k in additional income from winning it last season. I'd imagine a fair proportion of that is TV money and gate receipts though - the cash prize for the winners seems to be about £50k.
Good point that. Get some JPT advertising all over that side of the ground in exchange for a good paint job. Sponsoring the JPT Winners 2016 kind of thing
Bens interview other week I listened to mentioned a circa £700k dependant on the attendance at the final.