Just for kicks:
CPU: Well I can't even find an intel C2D 2ghz CPU anywhere, so forced to go with the T8100 at 2.1GHz instead. Not available for resale, but on e-bay under $150. And since we know that ebay is now more expensive then NewEgg, we can assume that this is overpriced. More like $125ish would be right.
GeForce 9400: Assuming this is the 512MB model, not 1GB. Non the less, price is $50 for 512MB, and about $60 for the 1GB.
160GB HD (lol at this btw). Assume a quality company, so lets take Seagate 7200.12. $40. If you prefer another manufacturer, $45 tops.
802.11n card. At best, $25. At worst, $75 for some of the highest end model. Can safely assume highest end is NOT in the iMac. So approximat about $45.
DDR3 1066. LOl at this too. 1GB eh? Couldn't find any 512MBx2 kits, so assume 1 stick, tops at $18.99. 2GB kits top at $38.99 btw, just for comparison's sake.
DVDRW - looking at only the 'slim' models, this still tops out at $70, and goes as low as $39. Apples Superdrive retails for $100 just for comparison.
OS - XP Pro for OEMs - $140
20"LCDs retail for approx $150. Lets be conservative and say a laptop LCD costs the same amount.
Laptop Camera: best options will run about $80-$100. Mainstream is