Publication in an ACM journal involves a lot more than just accepting a paper as-is.

Yes, it involves reviews by other experts in the field. Are those reviewers being paid by ACM?

Unrelated to the narrow task of file hosting, but entirely related to the missions of those nonprofit organizations. Some of the fees go towards the cost for hosting subsequent iterations of the very conferences the papers were presented at

While peer review isn’t perfect - it’s helpful. Arxiv isn’t peer reviewed. Most things in ACM journals and conferences are. That process costs money because it takes people and time to do it well. Journal subscriptions are often not enough to recover those costs.

As for sci-hub? They’re just taking the finished work. It’s like saying software shouldn’t cost much because The Pirate Bay can deliver software for free.

The reviewers don't get paid for doing the reviews in the peer review system..

I don't think the authors get paid either. So, no pay to authors nor reviewers. Does the editorial board get paid? Perhaps not.

> > That process costs money because it takes people and time to do it well. Journal subscriptions are often not enough to recover those costs.

Some of the items left to consider here are actually putting together the reviewed papers and publishing them. I would say the cost of these two items has gone down with the extended use of computers over the last 3 decades.

What other items are left? It would be interesting to know.