This highlights the problem of averages. Most (99.87% or so) humans download zero npm packages. But those that do, often download them in the thousands at a time. And yes, clean-room CI servers are a big part of that.

Perhaps npm could save themselves oodles of money by supplying a nice turnkey npm package cache and requiring major users to use it.

And perhaps the CI server folks would want this anyway because it would be vastly faster.

You might be surprised (or maybe not) to learn that many service providers are far more willing to spend money on predictably large bandwidth bills than on less predictable changes in their infrastructure which require human time and attention to implement.