I agree!
I sold an upgraded Bondi iMac Rev. A few days ago on ebay for $455 + $60 shipping.
Sonnet HARMONiG3 500 Mhz/FireWire,
256 mb RAM ( 2 x 128 ),
IBM DeskStar 120GXP 40GB HD,
Original CD, package,
Mac OS X 10.2 Retail,
Original Apple USB mouse,
Logitech Internet Navigator™ Keyboard.
So, the re-sale value will be better if you have all the original packaging. I would say about $1/ Mhz for the iMac.