Interesting when your product can be spiked, and make significant increases in profit. This looks like numbers that could potentially knock a business out of business. Reminds me of old phone bills.
My general point is: AWS is a business, and it operates as one. There are no hollywood style bad guys sitting there in cubicle dungeons on chests filled with gold thinking how to extract money, quite the contrary. It is understandable that customer cannot pay unlimited (from customers perspective) charges, but AWS pretty much incurs them, as customer being ddosed is consuming resources that would be otherwise be sold to others, or engineer time that would be put into developing new features and attracting new customers.
You can't disregard any business that doesn't fulfil that property as being "eventually unsustainable".
However my note was about general "traffic", if one sells video views for example, and revenues do not grow inline with adjusted to [almost always decreasing] bandwidth costs sooner or later that will become a big problem.