It is FAR cheaper to buy and maintain your own modem and router. I’ve bought an $80 cable modem less than once a decade. Last I checked, Comcast charges you about $8 a month to rent a modem. That modem I bought paid for itself before the first year was up and has kept on trucking since. Just make sure Comcast hasn’t decided to bill you the modem rental for your own hardware, because they will try and they will not refund your money for their mistakes.