The cost of plastic is insignificant to the cost of the tooling for these kinds of toys. If the units sold aren't in the 100,000's then a bigger chunk of the mold cost is applied to each unit manufactured.
My only concern when I bought the 20G model was the lack of remote play with my PSP because of the lack of the internal Wi-Fi module.
The last firmware update made it work through my network infrastructure.
Here's a small update to my Nu Galactica Model Blog. I'm still playing catch-up there but there is some new info. (The panel test was done back in September but I never posted my results.)
http://nugalactica.blogspot.com/
That Transformers trailer was quite nice.
On the Folding@Home front QJ had this news to report;
http://ps3.qj.net/PS3-triples-Folding-Home...pg/49/aid/87166
You will still have backward compatability dude. The PS3 is strong enough to do it all in software rather than with the old PS2 chip.
And frankly I wish they droped the 20G model from the US too. I couldn't find one when I had the money. I ended up spending anouther $50 just for an ethernet cable long enough to reach my wi-fi router. (It's plugged into the back.)
I imagine the price difference has something to do with average exchange rates. (That's a wild guess though.)
The truth is Sony craps on all of us equally.