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.
SP35 will make $1000 in BTC a month, now minus about $350 from that for hosting/electricity/cooling. $650 for the first month, then we have the difficulty jumps. At least 6 months JUST to get your money back. It's insane... (its even worse than this scenario, because of the delay in ordering this)
Now the S4, makes about $350 a month, minus electricity for that about $100. So let's say $250 a month is your profit. Its about 6 months to get back your initial investment if that with difficulty jumps. Wouldn't it be better just to wait for a larger miner since you will be even in 6 months?
Spending 1.5 BTC is really not that significant to me, you can make the same arguments it wont pay off, but as I said Prisma is just an experiment.