Most people wont buy a PC on Ebay. If they do they want a steal and will only pay used prices. You have no warranty, no return, and that's a low end weird build. There's no money to be made building PC's.anyway, and a bad build and Ebay make it impossible. People make money off the support, and a tiny margin on the actual hardware.
I highly doubt anyone would pay more than $600. You can't just charge someone double what something is worth and think they'll pay it