I'm not really bothered if united charge the same price for the league cup as they do league games, its a sad inditement of the club for me (one of many), when its likely to be reserve teams on show.
I also think my point is valid, I would expect an increase in price for a later round especially if it was against us or say Liverpool, (unless its a 2 legged semi final when there has to be an agreement between clubs).
If there was then a boycott by the away team, united still have to pay the away club the gate receipts, regardless of how many tickets the away team sell, so if none of the gate receipts come from away fans, are effectively doubling their loss on away fans by charging stupid prices. I know its not a lot of money in the grand scheme of things, but I'm sure united would quickly get sick of paying the away club gate receipts, if no away fans turned up, especially if every club followed suit (however unlikely that is).