I still find the choice of buying new 1080 Ti's for mining absolutely ludicrous. At least here in the UK. The absolute cheapest one is available for £675 here. Even if I got £200 per RX570 (I have 14) it would only allow me to get FOUR 1080Ti's.
Currently mining ETH+DCR makes me $32-35/day. 4x1080Ti's would make half as much.
Regular 1080's actually give you more bang for the buck.
699 usd per 1080 ti sometimes as low as 650 usd
you are at 868 usd
I can build a 3 card 1080ti for 2100 usd to 2250 usd
spend 550 watts get 1900 sols
earn 10 usd a day burns 14 kwatts a day about 1.40 usd
so I net 8.60 usd a day
I sold all the lessor gear at peak prices. I sold 1070's 100 more then I paid for each one and they all earned over 100 each.
basically 400 usd became 600 usd in under 2 months I sold 13 1070's
and I under cut the crazy high markups. when the 1070's were going for 600 usd on eBay I was selling for 475
so I netted about 2600 usd profit on my 1070's which was 4 1080ti's
By selling off everything but the 1080 ti's I did very well . the 17 1080ti's I have are basically all paid off. I slowly add to them.
If you are in the UK your chance to sell the 470,480,570,580 at 300 pounds is gone it was true about six weeks ago
I have said if I still had my lessor card I would not sell them.
As for only buying 1080 ti's now for my setup it works.
if your power cost is very low under 5 cents a k-watt 1080ti's are not that important as for mining eth I stopped that once you needed 3gh to earn a block at eth pool
http://ethpool.org/creditseth pool pays uncles and to mine eth and not get uncles is very costly.
back in the day I got 30-35 coins with uncles I would not mine without this.