I owned a 1988 Trek 1200. It was bit nicer than that with biopace chainrings. The bike was very nice though. It was a fast bike with a surprisingly stiff frame.

That bike looks good. It looks like you may want to change out the cable and housing. On a plus side, the tires look new. I would offer him $150 and mention the old cables. I'd also check out the chain to see if it needs replacing.

FWIW I bought my Trek 1200 for $125, which I considered to be a steal. Three months later, I listed it on Craigslist for $250 and got 3-4 interested buyers in a couple of days.

Also, knowing how to work on your own bike will save you lots of money. The LBS will charge you labor and parts fees.