I'm guessing $300 a month, maybe more.
If it starts to get really good I'm betting it will get even more expensive.
It sounds great - but for me it just means I'll be hanging onto my car until the wheels fall off.
FSD is already way more than I paid 2-3 years ago, so if I sold my car and bought a new Model 3 I'd be paying much more money for the same features. Just not worth it.
I dread to think what FSD is going to cost when my Cybertruck is ready for delivery, maybe enough for me to settle on basic AP.