Ah you missed what I said, as I clearly stated it as "above ground" transportation. Though I 100% agree with you that busses are the cheapest form of transportation.

But I was going for above ground. See, Busses always have to wait at stop lights and all that. Now, if Disney were to build their own stations for busses and have their own roads for the busses to use, I'd have no problem with the busses, but obviously that would drive the cost up to be even more expensive than a monorail system. Now boats, on the other hand, are nice, but water doesn't connect all the Disney parks. I don't even think it's possible to connect them all via boat, as the water levels differ greatly between lagoons and waterways. Correct me if I'm wrong.
Okay, what am I rambling on about?
Compared to light rail and above ground trains, Monorails are the
cheapest.