Just calculate price difference for electricity consumption let's say for 1-2 year and psu cost. Also, it's important to compare apples to apples, so it should be the same brand psu.
About 10-year warranties in some countries it's just a scam. You have to send broken unit to US or HK and pay for fedex or dhl yourself. So using in your calculations 10 year does not make sense.
As far as the calculations, it of course varies on the exact efficiency, power costs, etc, but even that $0.15 cent a day saving so many of you are poof-poohing, it still adds up to $54.75/yr. So even at only 4 years it would be nearly a $200 savings. I think spending an extra $40-$60 upfront is worth the extended payback.
Again, it depends a lot on your electric cost.
To "save" $1 a day for me would take a jump to TITANIUM power supplies from my current Golds - and would involve a few THOUSAND in outlay given how many PS I'd have to replace and their sizes.
If I moved my entire farm to Plat from Gold I'd only save 50-60 cents a day *IF* I was paying going rates for this area (I'm currently on a flat-rate contract) - presuming I could find Plat supplies that actually managed 2% better efficiency than my current almost-all-Seasonic mostly-X-series horde of supplies (Seasonic X-series are some of the most efficient Gold-rated on the market, and come bloody close to Plat efficiency in actual usage).
I also prefer the security of using a known very high quality lasts bloody near forever supply from a manufacturer with a VERY high reputation earned over a very long time, for *THAT* I'm willing to pay somewhat of a premium. The well above average efficiency is a nice little bonus.
For folks with electric rates on the high side of 10c/KWH it's a lot easier to justify going with good Platinum supplies over good Fold supplies.
At under 5c it's VERY tough to do so.
