So there are two take-away lessons here: First, power supply efficiency will only get more important for server builders, especially in gigantic datacenters like Google's. Second, someone somewhere is building 90% efficient server-class power supplies, and I want one. :)Another reason that Google builds its own servers is equally simple: it can save costs on power consumption.
Energy efficiency is a subject Holzle speaks passionately about. About half of the energy that goes into a data center gets lost due to technology inefficiencies that are often easy to fix, he said.
The power supply to servers is one place that energy is unnecessarily lost. One-third of the electricity running through a typical power supply leaks out as heat, he said. That's a waste of energy and also creates additional costs in the cooling necessary because of the heat added to a building.
Rather than waste the electricity and incur the additional costs for cooling, Google has power supplies specially made that are 90% efficient. "It's not hard to do. That's why to me it's personally offensive" that standard power supplies aren't as efficient, he said.
While he admits that ordering specially made power supplies is more expensive than buying standard products, Google still saves money ultimately by conserving energy and cooling, he said.
Here's the link: http://www.networkworld.com/news/2006/0 ... s-for.html
Hopefully we'll see a general increase in PSU efficiency in the coming years. 
Lifespan cost would make it pay for itself, but most consumers don't really care that much. The big OEM's that drive the bulk of the PSU market don't care at all, unless government regulations like Energy Star force them to. (personally, I think computer sellers should have to list the dollar value of the machine's energy consumption on the label just like refridgerators do)