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Why is the price so high?
Great question. Here's the open source 3D design I created from a real gear so you can print it yourself. thingiverse.com/thing:5758811

I don't have access to a 3D printer
Check with a local library, university, colleague, or friend. 3D printing has become very popular and accessible today.

Couldn't I just sell your model?
Please do! I specifically licensed my design so that the prices of replacement gears will go down.