$300 sounds fair to me. You will pay a little over 100 just for a working MC PCB. If the trackballs are the same as what is in a MC cabaret, those are a bit hard to find as well. I think it all boils down to if you want it or not.
Do you have a cocktail yet? Do you want one? I personally think every arcade should have one, but many just don't like them.
Some think MC shouldn't be played on anything other than a big ball. No cocktails or cabarets for them. I like MC, but I waited for a full size version, bought it for $150 broken..PCB is with BitSlicer right now