$0.08 /kWh is good price. If you buy the 6x R9 390 and a mother board with 6 PCIE slots, you might ROI.

PSU probably will cost a lot!

And if GPUs is easy to sell on ebay - PSU not

PSU is not easy to sell on Ebay, it can only get 25% of the original price. For the good graphics cards, the depreciation is low.

psu does not sell at 25% on ebay.

you can get 60% if all parts are included on quality psu's

here are some typical sales for used psu's

http://www.ebay.com/itm/Seasonic-850W-80Plus-Gold-Power-Supply-SS-850KM-Intel-AMD-ATX-PC-120MM-Modular-/182155134448?http://www.ebay.com/itm/Open-Box-Seasonic-ATX12V-EPS12V-660-Power-Supply-SS-660XP2-/131792955451?

if you are not a big seller on ebay fees and the like will cut into the sales prices but not as low 25%.

also people will buy them here for 50% or 60% if the seller here is good.