Yes thats a good price, the 7870 is a very capable gamer card and 2 years ago i would have enjoyed getting it for 1/3 the price. It will handle most of the 1080P stuff pretty well, prehaps a few settings lowered (dependable on game) but usualy very high details. The 7870 isnt just a solid performer but it got a (still) outstanding efficiency, there isnt much cards more efficient than that. It is very fine suited especially for SFF systems, because not to weak and not to powerful, its the perfect sweet spot between heat management and "solid performance", so it can be considered a "sweet spot card" when it comes to smaller systems. Of course, a heavy modded Skyrim (over 80 mods) with superior max graphic settings is a hard cookie to crumble, but my 7870 is still able to keep the game in a playable condition so even after 2 years of use nothing to moan.
As long as the used card is in good condition (no artifacting, instability or other issues) i think its a very good deal.