Yeah I agree with the above. I spot checked eBay and used 980Ti's are active in bidding, meaning a lot of people are dumping theirs, most likely after upgrading to a 10xx card. This is the case for all 9xx GPUs.
I do not see the value in a two year old GPU that was top of the line but now starting to show its age with GPUs half of its original price (this is always the case with GPUs, nothing new). Now if 980Ti's were going for $275-$300 right now, then I'd get one of those. And they will be that price by the end of the year as Volta approaches.
With that said, the prices of both AMD and Nvida GPUs are through the roof (in the US anway) thanks to cryptomining greed and them snapping up GPUs as fast as they are shipped to Etailers...