probably a couple of dollars a month, which would be very tough to actually make work. Even facebook only makes a few hundred dollars a year per person in the US.

the alternative is they'll develop some common mesh local network that'll grab data through any gateway. Imagine your tv connecting to some wireless headphones which have multipoint feature enabled and connected to a smartphone which has wifi, tv sends encrypted data to buds, buds to phone and phone to some external source. Ofc it can be more sophisticated but totally doable and plausible.

Or imagine some localized automesh based on zigbee/matter-> you have a philips hue lamp connected to wifi, tv connects to it and it forwards data... I totally believe this will be the next development of ad networks and sold as 'better smart home devices'. And it'll not require any LTE. Or it can have LTE only on some subset of devices while others will use that as gateway.