Well, here's 3PO:
I couldn't find a real good picture of 2PO.
Just to stay on-topic, I don't have numbers or a cost analysis, but I would submit that Division 1 colleges wouldn't pay an extra $1,200 or more if they weren't convinced that the extra official helped the game. Why don't the NBA and NCAA still use 2 officials? Because 3 clearly make for a better-called game.