Sometimes these deals do come along. If it is not too beat up, and even if you have to plow in a few $'s for a good tune up and some replacement parts, you still are probably ahead of the game.
I picked up a ConceptII rowing machine for my daughter for $100 last year. List - $800-$1000.00 It didn't even look like it was used one time. I felt like I was stealing it.
Good Luck.