http://www.www.joystiq.com/2007/07/16/scee-president-going-up-20-gb-is-not-worth-it/
When asked why there's no 80 GB PS3 in Europe (at about 3:40 in), he actually responds: "You know, the difference between 60 and the 80 gigabyte is very small. We just feel that going up 20 gigabyte is not worth it. If you're going to double it, it's worth it. So maybe you'll see something a little bit later, but 60 and 80? Really not much difference."
I agree. Gotta love it when Sony tells you the truth, though tries to sell you otherwise (NA).