Macs depreciate slower than PCs. When I'm done with my Macs I sell them and for a pretty good price. For example I've sold my 17" iMac G5 from 2005 (bought it for 1950$) just a few months ago for ~400$ - thats for a 4-year-old PPC machine in the Intel era.
Also, I've been scouting around for how much old MacBooks sell for and found out I can easily sell my late 2006 MacBook Core 2 Duo for ~950-1000$ (bought it for ~1900$). This is a 2.5-year-old laptop.
If that isn't worth anything, I wonder what is?
Ditto...i resell all my macs and usually recoup 90% of the cost or more