HardOCP has written an editorial about why 80Plus may be irrelevant when buying a PSU. The site not only explains whas 80Plus means but also describes how companies cheat, and calculates the operating cost of PSUs with 80Plus to 80Plus Platinum. You can read the article over here.
One of the important aspects to note about ECOS, and 80 PLUS® testing, is that vendors supply the power supplies and $2500 per unit tested. ECOS does not go to a retail location and select samples power supplies; instead ECOS relies on vendors to send products that are honest representations of retail products. Long time HardOCP readers will know of course what kind of problems this can cause. This makes 80 PLUS® sample submissions an area that is ripe for abuse. And to put it simply, it is abused; we have seen the same thing with testing samples here at HardOCP and it is not an inexpensive problem to solve.
Perhaps the lesser of the evils from this point is cherry picking PSUs from production runs. In this case, all vendors have to do during production runs of its power supplies is test enough units until it gets just one that gives the level of 80 PLUS® efficiency desired. Just one is all that is needed. Then the PSU reseller sends that unit off to ECOS just like it was a random unit that is an honest representation of a retail product and not the golden ticket. Unfortunately, since ECOS does not verify retail units after it tests a unit sent by a vendor, vendors have almost no chance of getting caught doing this. Who can blame these PSU companies for doing this when the watchman is asleep at the switch?