Say a PSU manufacturer really wanted to have the highest efficiency possible in a PSU. How far could they push it and what would they do to push it?

I'm asking because I'm curious as to what the future might hold and not because I was planning to learn everything there is to know regarding circuitry and then design my own PSU. I'd imagine someone else here might through.

Greetings:

I think this is an excellent question -- I have been wondering about this myself. Long ago, I read that computer power supplies were made in the way that cost the least -- but that there are more elegant and efficient methods of designing and building a power supply. Now, I'll bet things have improved since then, but I'm looking forward to any info about this.