I'll take it off your hands, I was actually saving up for a 5850, but i was looking on miner specs and you said you only get 170mhash, it states that it should be like 300+?
Model Price [25] Availability Avg. Mhash/s Mhash/J Mhash/s/$
5770 $136 Moderate 212.83 1.45 1.56
5830 $92 Moderate 302 1.68 3.28
300+ is with a decent overclock. I used to have several 5830's, and at stock speeds, they would do 220-230MH/s. My 5770 was the only one slow enough to go below the 200MH/s mark.
It could have to do with what miner he is using and what pool he is connecting to though.
Also, 5850's are being sold left and right for $60. $80 for a lesser card seems... overpriced. Just my opinion.