No idea but $30 to ship a single fan is absurd.
I agree. Look for some old server fans on that big auction website.
I prefer Nidec fans, but pick the ones you like.
For example a Nidec 4 wire, ta450DC 3.3A fan is capable of 220 CFM at full power (it does sound like a jet engine). But any good PWM (4 wire) fan speed controller can balance sound and cooling. These fans will give excellent pressure across any liquid cooling radiator, much better than stock. You may need some longer mounting screws since these are typically 38mm thick.
The best part is they are about $10 shipped and will run forever since they were designed for servers
Here is the spec on my favorite (its the 12V model)
http://www.nidecpg.com/fanpdfs/va450dcf.pdfSearch that auction site for 364517-001 (the HP model number)
Here is an example of two for $10
http://r.ebay.com/tzLipQAgain this is just my .02, and YMMV.