I totally agree with your first statement, but I think the extra money is buying so much more than just Blu-ray.
As I have said before, a 360 (like the Xbox before it) is basically a PC in a non threatening box. The hardware is almost out of the box (no pun intended) so it's familier for developers to program for. Therefore the games and graphics which are coming out now are pretty much the standard of things to come.
I beleive that with the PS3 however has much more longevity, as it boasts custom hardware so it will take developers longer to learn to code for it effectively. Also when you look back at games like GTA San Andreas, which completely filled a double layer DVD, then you realise that you need HD-DVD or Blu-Ray for new games if you want more content. If you have to buy a HD-DVD player as an add-on for the 360 then the difference in cost is falls.
I have my PS3 import arriving from Japan next week and even with postage it came to just over £280 and I will import games from the USA as they work out £10 cheaper than they would be over here.