Speaking of Joann's..... this week you can get five Olfa 45mm blades for $16.99 without a coupon. That is about $20 less then they usually charge. I don't know if this is online too. It's coupon commotion week. I bought two packs, should last a while! I find the Olfa blades last a long time.
I looked and the price is good online too:
http://www.joann.com/search/_olfa_blades/