The biggest cost isn’t the sim card, it’s maintaining all of the backend infrastructure, security, software etc. which enables it all.
I’m pretty sure most cars don’t have their wifi on when they are parked/sleeping/off to save power and prevent phantom drain.
The Tesla is ‘woken up’ via a command over the cellular network and it then connects to WiFi if available. You can communicate it via Bluetooth but that’s only basic commands like lock and unlock.
Pretty much all cars have a lime limited free period on their connected services. I’m pretty sure standard connectivity in my Tesla is included for 8 years now (early cars it was lifetime but that ended in ~2019). Premium connectivity is only 30 days and after that is £10/month.
You don’t need the latter mind and I’ve never paid for it. But standard connectivity is basically essential, 2/3 of the screen is dedicated to maps which stop working. You can hotspot your car to another device though so you wouldn’t necessarily need to hand musk a monthly fee.
Other cars are far worse though, I’m pretty sure polestar only include connectivity for 3 years at which point the built in nav stops working.
What car is it that you are talking about?