The grandparent's argument is that AWS is extorting the customer to remain a customer by making the cost of moving data out of AWS prohibitevly high. I don't think it is actual extortion (at least legally), since the egress prices are public, and you could argue if the customer had done due diligence they would have known the price when becoming a customer in the first place.

But if they had changed the price after a customer became sufficiently invested in AWS, that would be using "unfair means", to obtain the customer's continued business.