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?
Why not use 400 USD/BTC as it is right now? Is your magic crystal ball letting you know that in 1 month the exchange rate will rise?
Ah, I see. Those are extremely poor numbers. The Prismas are a hair under $6000 right now, so that's factoring in $3250 for 10kW of power supply which is ridiculous. Even if you don't want to mess with server PSUs, you could go buy 10 well reviewed gold ATX supplies (RM1000/Capstone 1000M) for $1500 shipped from Newegg (plus tax, if you're unlucky).
Ok, with the updated numbers you will have an advantage of $1500 for all lifetime mining profits for buying AM Prismas vs 2xSP35 at the cost of needing a bigger electricity circuit.
Right. Assuming the Prismas' are $1500 cheaper and you'll mine ~$800 before the SP35 ships (start mining Oct 15th, end mining Nov 21st, 10c/kWh, 15% inc. per jump with a 5% lowering per jump), that gives you $2300 in hand with the Prismas vs the SP35.
From Nov 21st onward the difference in power is 11kW vs 7kW, so 4kW. There's 8760 hours in a year, so at 10c/kWhr it would take 2.62 years for the cost of powering the units to make up for the price differential.
At 15c/kWh, the numbers go down to 1.4 years of running before the difference in price is made up.
At 20c/kWh, don't bother. At the current price and next estimated difficulty (~35B), the network only has to increase 50% in size before you're at breakeven for power with $400/BTC which it very likely will be by the time you get your Prismas.