Geeze, is everyone mining ETH with their 290x cards or something? Those almost 300W cards can't be good in terms of energy efficiency... Just sell one to me instead!
Nobody is selling any GPUs because they are very profitable at the moment.
Efficiency doesn't matter at the moment because its makes a few times over most people's electricity rate anyways.
You can probably buy a brand new 390 for a similar price as used at your local micro center or newegg.