Good question. I am not sure that anyone has measured it but you can calculate it. It obviously depends if your connection is high speed or goes up and down in bandwidth.... but here are the general assumptions assuming highest quality at east level of the camera:
360p—300MB of data per hour
480p—500MB of data per hour
720p—1.5GB of data per hour
1080p—3GB of data per hour
Your webcam is likely the 720p and it likely won't use up anywhere close to 1.5GB but that's the worst case scenario.
You can also test it for 6 mins with the a friend using zoom, skype, etc and see how much data was sent. You can see it in networking.
I would guess you will use under 3GB for the test and definitely under 5. Anyone has a better number?