I buy generic blades online from SouthStar Supply. I get 10 - 45 MM blades for 19.99 plus shipping. This last time I bought 20 blades. With shipping this cost about $49. This is about 2.50 per blade. I have been using them for years.
http://www.southstarsupply.com/catalog/
The Olfa blades on Joann's are $60 for 10. So even with a 50% off coupon it still costs $30.