I don't see how you can argue with the courts that the bandwidth cost to serve a 100mb zip file is $4. That's beyond egregious
Choosing a price based off the cost is just one pricing strategy. Another is to do it based off the value it offers a customer along with the price competitors are charging.
They're not even serving the file. That cost is born by the external provider.
The four dollars is for providing the platform that the user used to navigate to the link and download the zip file.
That's a fun bit of argument from the owners of Chrome.