and you would need 2 at a buck forty each,
Ah, one would accomplish what the OP wanted, to be able to switch betwen two sources to one monitor. The two video sources wire to the NO and NC contacts, the monitor wires to the common contacts. One pole used for the active signal, the other pole for the ground side.
I don't have a problem with anyone building a analog switch, just think the relay is a quicker simpler solution. It's good for the OP to have choices.