It's incredibly common to see misconceptions between modems, gateways, routers, etc. I think this confusion is exacerbated by the fact that Comcast and most other coaxial cable (even if they're fiber, if the output is coax to your unit, it's going to be coaxial for this purpose) systems.
Comcast/Xfinity offers combination devices, which include a wireless router and a modem, in the same box. The only thing you need to connect to a coaxial broadband network is the modem. This is freely available. The only catch is that unless you buy a combo device like what Comcast gives you, you still need a wireless router if you decide to buy your own modem. You should probably do this though, because combo devices that include wireless routers tend to age poorly (thermally).
A modem will speak DOCSIS 3.1, which is a protocol that gives a lot of trust/control/authority to Comcast. They effectively can push updates to it, configure it, remotely administer it, etc. However, these are NOT functions they have if you buy your own router and connect it to the modem. If you go this route, you have full authority over your LAN and you can do whatever you please. The only thing Comcast can update is the stuff that speaks DOCSIS -- the modem.
The catch is that with the combo devices that they ship out, those devices include remote administration and firmware control for the entire stack. They can remotely push everything.
I don't like to be pedantic, but this is critical. DOCSIS 3.1 modems that aren't combination devices cost just as much as good wireless routers, if not more. So $100 isn't a good estimate of what most people would have to pay, unless they already have a router they'll use. It's going to be the cost of the modem and the cost of the router. The upshot, obviously, is that you can really spend a lot of money and go all out (e.g., buy a pfSense router, UniFi switches, access points, and a good DOCSIS 3.1 modem, and have a really nice LAN), or you can opt for a budget router instead. You get to pick one of the most important pieces of the equipment -- the router -- instead of being stuck with what Comcast gives you (probably a used/preowned combination device).
Comcast/Xfinity offers combination devices, which include a wireless router and a modem, in the same box. The only thing you need to connect to a coaxial broadband network is the modem. This is freely available. The only catch is that unless you buy a combo device like what Comcast gives you, you still need a wireless router if you decide to buy your own modem. You should probably do this though, because combo devices that include wireless routers tend to age poorly (thermally).
A modem will speak DOCSIS 3.1, which is a protocol that gives a lot of trust/control/authority to Comcast. They effectively can push updates to it, configure it, remotely administer it, etc. However, these are NOT functions they have if you buy your own router and connect it to the modem. If you go this route, you have full authority over your LAN and you can do whatever you please. The only thing Comcast can update is the stuff that speaks DOCSIS -- the modem.
The catch is that with the combo devices that they ship out, those devices include remote administration and firmware control for the entire stack. They can remotely push everything.
I don't like to be pedantic, but this is critical. DOCSIS 3.1 modems that aren't combination devices cost just as much as good wireless routers, if not more. So $100 isn't a good estimate of what most people would have to pay, unless they already have a router they'll use. It's going to be the cost of the modem and the cost of the router. The upshot, obviously, is that you can really spend a lot of money and go all out (e.g., buy a pfSense router, UniFi switches, access points, and a good DOCSIS 3.1 modem, and have a really nice LAN), or you can opt for a budget router instead. You get to pick one of the most important pieces of the equipment -- the router -- instead of being stuck with what Comcast gives you (probably a used/preowned combination device).