I am a total fabric snob. I categorically loathe synthetic fabric and will avoid it if at all possible, and that makes my stuff probably run a little higher in terms of cost, even with coupon shopping and hitting the LA fabric district up and bargaining like hell. Beyond that, I've dyed fabrics fairly often for cosplay, plus one of the ones I'll have used about three yards of dupioni silk at about ten a yard ... So I'm looking at anywhere between about seventy and almost two hundred each for the three I'll be wearing to Kcon. Wigs definitely drive the costing way up, as can shoes. Having to drive nearly an hour to get to JoAnn's doesn't help, either, as does the fact I can't really alter things for most of what I do, and I'm too neurotic to do it anyway, so thrift stores are pretty much out.
Miranda (D.Gray-man) is actually my cheapest cosplay to date, or will be once I finish her -- probably because there's no wig involved, and I already had the shoes. She's run me about seventy dollars, mostly in fabric, with some for dye and associated chemicals and about five for a clock key. Risai is my most expensive so far, at about a hundred and seventy (or probably a little more).
(Next year is going to be my Year of the Insane Cosplay Expenditure, though. I'm doing another Juuni Kokki cosplay that will involve leather armour, and my Trinity Blood cosplay has already cost me about two hundred in supplies -- which isn't quite all of the fabric, and none of the resincasting or armour supplies.)