The cost is all in the distribution/packaging - the covers themselves are surely injection molded, pennies if that per cover, and lots of covers fast. (Injection molding tooling costs like 50k+ to setup, obviously not a concern here).

If the cover costs .05$ (which I bet is 5x it's cost) - the rest is all of the packaging/printing/logistics/shipping/etc.

My question is if a solution so cheap is available, why can't they just fix the root issue of the keyboard?