It doesn't work like this. If paypal's customers decide to cash out as a whole, then that means there is a net sell. There won't be enough buyers in paypal to

It doesn't work like this. If paypal's customers decide to cash out as a whole, then that means there is a net sell. There won't be enough buyers in paypal to cover the sells. They would need to expose themselves to another market by buying / selling actual bitcoin to be able to float like you describe.