Well, if you want one of the "100ft" or "160ft" delrin spools (although you probably want to remove some of that length so the spool is easier to clip off -- they're sold overfilled, IMHO), you can get decent ones from Dive Sports for a ScubaBoard-special $15 each:
http://www.divesports.com/mall/divesports_acc_fingerspoolSPC.asp
I couldn't come up with a good reason to buy any of the prohibitively expensive aluminum, stainless steel, or brand-name delrin spools when I saw those. If I ever have one of them break on me, I'll have to post about that, but I don't expect to have any more problems with them than any other spools I have.
For a primary cave/wreck reel, I might justify going with something expensive (and worth it), but there's really not that much to a spool, eh?