No gpt18Pro won't cost $1Bi dollars. The buck (or the bubble) will stop somewhere.
I'd be more worried for the people making trades run 1ms faster, they literally create no value to the world that is not something their own peers believe it
There are billions of people not knowing and not caring about what is chatgpt and while it might hit them hard, humans are more flexible and less impressionable than most people think (I mean, some people think it's the other way as well and they might be right in some situations)