Performance equal to a GTX 1660, which is regularly available for about $200 new for the cheapest model
Consumes about twice as much power as a GTX 1660 (120W vs 250W)
Used instead of new
No warranty for the buyer
Nvidia's drivers do not support "G-Sync Compatible" (ie: FreeSync) for cards prior to the 10- series.
Can you get something for it? Absolutely. For someone who wants that particular level of performance, AND has a PSU that can deal with the 980Ti's power demand, and does not care about having FreeSync (or doesn't have or plan to get a FreeSync monitor), about $150 is the max I'd guess. Though I think that might be slightly optimistic.