I just got 4 Yate Loom 140mm fans from Petra's Tech Shop for 4 for $23.96, $32.94 shipped. Great fans BTW.

http://www.petrastechshop.com/14yalod1cafa.html

Great fans except for the shitty bearing, meaning you need to relube them every year or so, or replace them later. Either is an option but the problem is that it's not so easy to find a decent quality 14cm fan to replace it.

Then again I suppose if you'd bought a PSU with the odd 14cm fan in it and found the PSU fan already failing, this might be a change to replace that at lower than avg. cost although it'll have to be grafted on, not the right connector for most PSU fan circuit headers.

These would be great fans except that in my application, I was installed them mounted horizontally. With the crappy bearing that dave_c is talking about, they produce a clicking noise. Not quite the silent fan I was looking for. For now, I have them powered down enough with my voltage regulator that it's not a problem, but just a work of warning if you're buying these and they may go into a case mounted horizontally. I only paid $5/ea shipped, so I'm not complaining too much...anything better for my needs would be $15-25/ea.