Couple of points.
I sold a 99 R800 last year for 5 bills, in excellent shape.
I bought a 2006 Alloy Synapse for $650 at the same time, 105 equipped. I think 750 is high, but it's all moot if you don't know if it will fit you. If it truly has a 1" headset, it 2000 or older, 9-speed. You need to ride it or a similiar frame to see if it fits you, that HAS to be the first consideration, then deal, good or bad come next.