In looking for an extra computer for home office, I've found that most sellers have been charging outrageous pricing for shipping a PC without a monitor.   If you look at Dell or HP's web site, shipping of a computer AND 19-20 inch monitor is $49.00.   Most manufacturers will ship free for some systems. 

For what ever reason, sellers here on E-Bay think $89 - $129 for the COMPUTER ONLY is fair shipping.   I think that's pure robbery.  The rules of E-Bay state "REASONABLE HANDLING FEES".   Since when is $50.00+ a reasonable handling fee.   

Lastly, Check the manufacturer's web site on the PC you are looking at bidding.  Many systems that look like deals on Ebay might be cheaper with a full warranty from the manufacturer.

Example:   Dell 9150 2.8 Ghz processor, 512 Meg Memory 80 GB Hard Drive sells for $450 from Dell.  Many people are selling it as a 9150/XPS 400 (which are not the same) for $539 plus outrageous shipping!

READ CAREFULLY the sellers ad.  If the PC does not come with an operating system, there's a reason... they don't have the original OS from the system manufacturer.   Most times, the retail version of the OS will not work as it depends on drivers from the manufacturer.  When this happens, the setup crashes and will not continue.   You can count on spending $250 for the OS with the drivers to get the system booted from the manufactuer.

Also be aware of scratch and dent sales!   I've seen some of these systems look like they came out of the war zone in Lebanon or from the wreck of hurricaine Katrina.

BUYER BEWARE!