I haven't done any sort of research on the matter...but if memory serves........
I think I'd agree with the initial post that it's the F.A. who regulate the ticket prices for the games.
I think It may also be that the gate receipts from the game are split three ways, a third each to both clubs and the F.A. retain the other third.
I don't know how, or if this may apply with any T.V. income but I'd imagine it's on a similiar line as the gate receipts. After all, the F.A. have to raise the income for their prize monies, but I suppose with respect to ticket costs, I'd assume it's a case of the higher the profile of the cup tie (i.e. the further the club progresses in the competition), then the higher the cost of admission........
I may be wrong and if so I will stand duly corrected
However on the gate receipts front, then after feeling our may chance have gone after the Barnet drawn game (Ref & all!!) a full house on Saturday will result in more cash going into the club's coffers aiding the club in it's efforts to get financially solvent, the extra few quid in my eyes is well worth it, especially if it results in being able to keep hold of our rising stars and strengthen looking to move on and up League Two !!!