what is the cost for the foot?

Then please call the Apple Store. We don't have access to that information.

FYI: These are user-only forums. This is not Apple Support. if you need to contact Apple Support, then contact product and tech support:  Contacting Apple for support and service including international calling numbers.

These forums only provide help with Apple products. Thank you for your understanding and support.

I had one replaced once, and the cost was US$10 each, Installed.

That may or may not be the price today, but all Apple parts include installation, and parts are not sold any other way.