How do you figure the SP35s are cheaper? The price on 10 Prismas is 14.9BTC or 5960. To that you need to add 5*($45+$60+$3.50*8 + $10) for a DPS-2000BB/breakout/cables/shipping = $665
That's $6625 for 10 Prismas, which unless the SP35's have had a large price drop recently is still cheaper than two of those.
To be fair to RoadStress, I used $180 PSUs in my calculations and the price of bitcoin is fixed at 500 USD/BTC. Also, 2000W wouldn't be enough to run 2 Prismas. I don't know whether those server PSUs have the necessary PCIe cables so I was hesitant to use them in the calculations.
Can you provide some links to those products (DPS-2000BB/breakout/cables) so people will know what to look for?
Sidehack sells breakout boards and cables for the price listed. Not sure if he has stock now, but it's not like you're getting these immediately anyway. The PSUs are all over eBay.
http://www.ebay.com/itm/IBM-24R2711-BladeCenter-2000W-Power-Supply-DPS-2000BB-24R2710-/311083483747?pt=US_Server_Power_Supplies&hash=item486e0542632000W would be enough to run two Prismas. They've said 0.67J/GH board wise, which is about 1000W@1.5TH/s. It's running them full out, but they will handle that without issue. I believe Sidehack has load tested them continuously @ 200A.
Re: the $500/BTC, we're all hoping but it seems rather sketchy to base the numbers on that since you can't order an SP35 using $500/BTC without a time machine.