Although few here would pay $495, that is about the going rate for a 620 from the mid 1980's. Some on ebay have gone for more. Not an outrageous sum for a legendary touring bike.

I am not racing, so the DT shifters work fine, even when climbing. You may be able to go to a 7 speed cassette and find a set of used brifters if you wanted to modernize the bike.