I think I sold my HD6770 for around $35 or something, after shipping it must have been like $20. I only offered it because I was getting rid of quite a pile of components. It is around a 7750 in performance. (or is the exact same GPU, I can't quite recall)
800/1125 on the clocks means it's a 7730, the least expensive and desirable of the 77xx series. It apparently is the DDR5 version, so that's something you can mention to a buyer. It's the equivalent of an R7 240, so look for used 240s that have 1gb DDR5 and undercut those prices slightly.
I bought a pair of HD 7800 2GB DDR5 for 80$ on ebay, so I think 30-50$ is a far more realistic price. start at 40$ and lets them bid on it. you might get lucky if the serial number of the part of the video card is needed by someone trying to do crossfire with one they have.