Yes, but your talking new. Once you drive a computer part off the showroom floor you loose a nice chunk of it's value.
I too would pay $300 for it. It's a low end system. Hell, I'd probably buy it for the DVD drive and use the rest as a linux server. Can't play games on it.
Don't feel bad. This is the way technology works. The system I built a year ago for $1500 is now worth about $1000.