How much is this going to cost me

See if anything here helps 

Face ID on your iPhone or iPad Pro.  *

Face ID - If an alert says has been disabled on your iPhone or iPad Pro.  *

If Face ID isn't working on your iPhone or iPad Pro  *

Face ID not working.   -

Face ID not working' problems on iPhone.    -

Face ID Not Working.   -

You may need to take it in for service.

Genius Bar Reservation  -  US.    

Find a store.  -

Authorized Service Provider.  -

ASC YouTube for how to to schedule a repair at an Apple Store or Apple Authorized Service Provider – Apple Support

How much is this going to cost me 

To fix Face ID on my iPhone

We don't know, see -> iPhone repair and service -> iPhone Service & Repair - Apple Support

• Use our “Get an Estimate” tool to review potential costs if you get service directly from Apple.