Do not limit yourself to one "must have' game
have a list of 5 or 6 machines that interest you, then you can wait until one of them pops up for sale

also, do not think that a game has to be expensive or fully restored for it to be fun
I have just as much fun from a $2000 machine as I do from some of the more expensive games
dings and scratches add tot he character of a machine! ;)