When you find a great price on rotary blades by enough to last you for years! About 10 years ago I found an Ebay seller that bought surplus from a warehouse and he was selling the blades 144 per box! He had no real idea how they were used in quilting, concentrating more on the saw blades he had to sell. I bought two boxes and paid $30 per box. Now I could kick myself for not buying more but back then that was a lot for me to spend on blades. LOL.