If the gates charge for mass, and the price is high enough to make running trains and other transports through them a useless waste of time, imagine then how much it would cost to run a Rheinland Battleship through it. Now multiply that cost by the number of ships that would be in a fleet.
I note that I don't know why I'm arguing.
Edit: It would be a nice way for bountied fighters to escape pursuing battlecruisers...