Let's call 1.47BTC $600 and $100 for a PSU. That's about 50 cents a gh. I paid about 65 cents a gh on the S4, but it's more efficient. A wash maybe?
Depends on your power costs, but I think the difference between 0.69W (S4) and 0.75-0.78W (Prisma) would take a long time to make up for the difference in price.
PSU (and controller too) is indeed an extra cost but not for everyone. I'm reusing my PSUs and have spare USB ports on on some cgminer-capable hardware here, so I'm saving money on that.
Another factor is resale value, I think S4 has the advantage here.
Since I am batch 1, I will post AMPs/Watts used and other information so we can compare to S4. Not sure how they can be the same one when is 1100W and the other is 1400W.
But one is 2 TH and one is 1.4 TH. You have to break it down.
Right, I just bought one prisma for experimenting. I already know what the S4 is, and I didn't want to pay over 3BTC and wait 6 months+ for ROI.
Then really, you don't want it for different reasons.
Now if you want to go real big, this is really the winner I think:
http://www.spondoolies-tech.com/products/sp35-yukon-power-november-batch-1But the S4 is about as big as I want to get.
If you do the math you will realize that the AM Prisma is a much better deal than the S4 and the SP35 is not even comparable.
S4 is $1250+150 shipping so about $700/TH compared to the AM prisma at $500/TH.
The difference in efficiency is about 100w/TH.
At $0.1/kwh 100W would cost $0.24/day or $87.6/year so it would take more than 2 years to make up for the cost difference.
SP35 is also $700/TH but it is shipping a month and a half later than the s4/prisma so it really doesn't even compare.