This really is quite funny. I'm calling it now: that mount is going to cost you as much as a decent 3rd party webcam.
This is the sort of product that I would've expected Apple to put out just around when they introduced the touchbar and removed every port off their laptops. They know their laptop camera is crap, but rather than fixing it, they've decided to build an entirely new, overpriced dongle to solve the problem they themselves created. It doesn't even pass the sniff test. "You can use your phone as your webcam!".... ok, now what happens when I'm on a meeting and need to look at my phone? "Well what we've got another dongle that projects your Apple Watch onto your macbook so you can use it as a phone!"