A lot of those early "videogames over broadcast medium" worked by having all the games being broadcasted all the time in a loop and the decoder (typically a fat "cartridge" with a modem embedded) waiting until the chosen game was broadcast and then caching that broadcast into some (battery-backed?) RAM or rewritable ROM.

It was purely one-way communication, so payment and access control (if any) was handled locally by the cartridge. As far as I know none of those supported per-game payment, so the payment was included in the purchase/rental price of the cartridge/modem.