Did you buy at a fabric shop? I found my 2 ginghers off ebay with replacement blades for $20 each (set).
But the local fabric shop they are $80 and $70 at JoAnns.
I'm hoping to find more, I'm buying for 2 daughters now.
Bought all 4 girls a starter sewing machine, but 2 won't even learn how to turn them on. Maybe one day.