The upgrade is not too bad actually. DDR3 is very expensive. Man, I am really leaning towards the 2.53 option now. It actually doesn't sound so bad relatively speaking.
Coming from someone who once spent $649 for 16mb of RAM for my PowerPC 9600/350MHz back in 1996... $140 to MAX out the RAM seems pretty good to me. But I'll be there will be cheaper prices hitting the market very soon....