I actually work in wholesale used PC sales with Apto Solutions Inc based in Atlanta, and generally used PCs are sold based upon a price per MHz. Pricing varies on screens quite significantly, but Pentium 4 units (wholesale) generally go at 5.5 cents per MHz. That unit in the wholesale market could possibly go for $165, but if you sell just one computer to an end user you should get a higher return.
Let me know if you have any more questions.
Apto Solutions Inc