My electricity price is high. So I use the platinum power supply and also a big specication PSU, so that the efficiency is high.
Saving 1-2% over a gold PS isn't a big deal if your electric price is DOUBLE what most bigger miners are paying.
I suspect my electric would cost less if I used an 80% efficiency power supply than yours would for the same rig using a TITANIUM (93%+) efficiency power supply.