Have you seen this tip? I read about it on KarrieLyne's blog and had to check it out.
Harbor Freight sells replacement blades for carpet cutters for $1.79/pair. The blades fit in my 45 mm Olfa rotary cutter. (I've heard they fit other brands too.)
I picked up three packs, so that's less than $6 for 6 blades. I think regular price at Jo-Ann's is $6.99 for one blade. Quite the deal!
Before you place an order online (shipping was going to be $6.99), be sure to check the store locator. Surprise! There was a location just a few miles from my house--right on the way to Sonic so I could hit happy hour for a ginormous Diet Coke afterward.
I tried out the cheap blades today, and they seem to work very well. I'll need to test them out longer to be sure, but I'm pretty sure my days of buying their more expensive counterparts are over!