Since RAM is currently really cheap (4GB of DDR2-800 for my PCs cost me net. €60) I bought 4 more GB for my G5s. DDR-400 RAM is unfortunately a little more than double the price of DDR2 (4GB @ €150 net., because it's just not used very much anymore.
Just for kicks I looked at the german Apple Store prices. 4GB would be €670 net! That's 4 1/2 times as much. I wonder if this is a historical high water mark ?
I pity the non-techy buyers that get so ripped off.