This must be new. It's been about 8 years since I've had Xfinity but I always had my own modem and router and got a discount (i.e. didn't have to "rent" the modem).

Iirc it was something small like $5 or $15 a month... I really only did it for the better hardware and software.

This was earlier in the year, we had started hitting the monthly data caps on our plan and getting penalized.

I went in and the unlimited plan was about $15 less per month using their modem/router than my own (which I already had), plus the router was free (I'm not paying a monthly equipment "rental" fee).

One annoyance was that their router didn't allow spaces in the WiFi password, so I had to reconfigure all my devices.

I could set up the router in bridge mode where it acts like a dumb modem and continue to use my own router, but I have not bothered with that.