Our Fridge in our RV is the typical size RV Fridge, so it's not huge. It is however large enough for us to have 2 Ice trays and a small bucket that can hold about 3 trays worth of ice. Before we depart, I ensure the bucket is full of ICE and the trays are full with ice ready to be cracked into the bucket. Then as we use the ice, we crack the trays and fill em back up. I guess we just don't go through that much ice where it's ever been an issue. I can see, however, where someone might want that extra production of ice though, particularly if you have a cooler that you need to keep filled.
I haven't had to buy ice at the fort, but from all I have heard/read, It sounds like that if I ever need to, that I'd be better off going to the meadows instead of using the Ice Vending machines.