Hello, I've tried all of the above, and it still doesn't work.

If you are booting macOS normally and the camera hardware is not seen, then most likely the Display Assembly will need to be replaced. There is a slight possibility that macOS is corrupt or missing the camera driver so you can try to reinstall macOS over top of itself or even better perform a clean install of macOS by first erasing the whole physical drive before reinstalling macOS (test the laptop before migrating or restoring from a backup and before installing any third party apps).

If this does not help, then you can use a USB camera until you can get the laptop repaired.

You can contact Apple or an Apple Authorized Service Provider to examine the laptop to provide you with a repair estimate.

The instructions posted above are the best results that I can think of as well. As for the cost of what it is going to cost to get it fixed, we can't tell you that. It's something you're going to have to take to the Apple Store or get in touch with Apple Support and have them check things over and give you an estimate of what it would cost to get it fixed. We aren't employees of Apple and have no affiliation with Apple in any way. We are end-users like yourself and volunteer our time to come on here and assist people if we can to try and get issues that may be corrected without having to take the computer in for repair.