For those of you who use wisps...
http://woot.com/
48 pack for $10 shipped puts these at 21 cents a brush. If you buy 3, the shipping stays the same so you're looking at $19.97 which comes to $0.14 per brush.
These tend to come to $0.49 per brush in stores and $0.27 on other websites at times.
...and for those of you who do not use wisps: That's nice.
(This deal will end sometime today)