I think Leon hit the nail on the head with the question, "If it gets away will you kick yourself?"
I got a 15-91 in a cabinet for $5, but I had to drive 150 miles to get it. if it would have been next door I would have gladly paid much more. $80 seems to be mid range for what I have seen lately, so for me it would be the condition, especially the wires going into the potted motor that would make up my mind.