They actually used to be pretty good value for money, like 3 years ago.
Now Nvidia just wipes the floor with them. Apparently Nvidia's just been sandbagging most of the time, ie. the 980 & co. weren't the best tech Nvidia could have put out to the market however they knew it was so much better than what AMD could offer so they just went with the most cost-effective option for them.
The 1080 has been in the works for some time now, however AMD has no way to match it so Nvidia could of taken as long as they like with it.
My current computer used to have a AMD as a GPU till I finally gave in and got myself 970 (not the best but will do for now) even though the 1070 is pretty much the same price like mine is currently.
Mine is 360 euros, 1070 is same (when I checked the main thread), I should have waited but I was in a hurry... And idk if my PSU would be able to run it.