This is an odd question and while I do agree with Robert's point that this isn't really suited for this site I do buy an AWFUL lot of disks and I never thought I'd see a post where someone said they were surprised how cheap FC ones were :)
Well firstly I have to say that FC disks have always been staggeringly expensive compared to anything else. This was always due to the 'enterprise' nature of these disks rather than the actual transmission method, they're always built to last forever and can run 24x365. That said FC disks are slowly being phased out in favour of SAS disks purely because of the price differentials introduced now that the volume of SAS disk has got so high, the more they make the cheaper they are to make etc.
As to why the ones on your search are cheap, well that's a different matter. Firstly many if not all of those disks are for very specific disk arrays, not even current arrays either, and some may be refurbished and almost all won't have the regular (in the UK) 12-36 month warranty. Essentially that's a bargain-bin look at FC drives, if you go to HP/EMC/NetApp etc. and ask for quotes for new ones of those disks you'll find your quote will be MUCH higher than those prices.
Could you make an array of these, sure why not - you'd need to buy new mounts for most of them as they're in custom ones and buy an FC controller but yeah, it'll work.