I bought back in september 2017 5 RX 570 8gb Sapphire Nitro + (the best RX 570's and 580's on the market right now IMO) to complete my rigs. i paid for them in refurbished state (they were like new no problems at all), like 220€ each, around 250$ from the biggest retailer here in Spain.
They worked in a room of my house with temps between 20 and 40ºC. the only card that needed to rump up the fans was an MSI RX 580 8gb Armor that needed just around 65% to keep it below 70ºC working operation. Most of the RX 570 nitro+ need just about 40% fan to be around 50ºC working temps.
Now, on Ebay, there are authentic bargains. Brutal ones. I had the oportunity to buy 4 RX 570 sapphire Nitro+ for just about 80€, 90$ more or less. Brand new, in the top of the madness January-April 2018, this cards, brand new were above 300€.
So prices are going down. I had an emergency plan considering the worst condition i could think off back in November 2017. I knew the market would collapse. my contingency plan considered the market to go down by 70%. Never thought it would go below that. It went almost 90%, which left me with no time to reaction.
If (for me it's very unlikely), the market just pumps and holds for some time, we will be seeing our cards gaining huge value. But mining nowdays makes no sense at all. Specially now that summer is comming. In Spain, i live by the see, and the have lots of humidity and high temps, some days, above 40 with temp sensation of over 44ºC so mining is not an option unless it's really profitable, but it's not.
But we can see some kind of stabilization in price from the September 2018 after the selloff . Maybe it is a good time to buy some new not overpriced cards now.