I've just had a paper accepted last week in a traditional journal (peer-reviewed and paywalled) and I'd share a few things I know and feel about scientific publishing from an anthor's perspective.
The publisher provide a valuable service to authors. Their online submission protal was a joy to use and their staff very friendly and responsive. Once a panel has decided that my submission was at least fit for further consideration it was forwarded to three peer-reviewers who may and may not be reimbursed for their time. After several rounds of comments and changes, the accepted draft was sent to a publishing house in India for typesetting and proofreading (They've done a very thorough and professional job with it) before it was ready for print. There are a lot of man-hours spent of making this happen and if the hours were billed individually it will add up to a pretty hefty sum. Earlier versions of this paper had been submitted to other journals and were eventually rejected - more hours of work done without output.
Open access journal such as PLOS ONE charges a non-trivial sum ($1500 and up) to cover these costs and all I could say is that you get what you paid for: How much does a good lawyer/consultant charge per hour? Most people only submit to OA journals if they are ideologically compelled or have ran out of other avenues.
The quibbles between Elsevier and librarians is actually an old one (the article linked below dates from 2003) because they own a number of high impact journals and can bundle less popular titles with high impact ones to increase their margins. While this is a pretty underhanded tactic to use, these less circulated journals would probably have gone out of print without the practice.
http://www.nature.com/nature/journal/v426/n6964/full/426217a...
Piracy has been around as early as universities had been around. There were more than one usenet groups dedicated to these activities and reddit's /r/scholar remains as its latest iteration. I was quite active on a medical forum where doctors and academics help each other out with paywalled papers on a quid pro quo basis. (Doctors are probably the most affected since their job requires access to latest research articles yet few hospitals have the budget for it unless they are affiliated with a university) All because there will always be a few odd journals that are not covered by my university's subscription but others might do. Publishers mostly turned a blind eye because their use are limited to a small group of people who cannot be persuaded to pay anyway. Sci-hub is something different since it is much more accessible and comprehensive, which threatens the current business model of publications.
P.S. This thread from another HN front page submission offers an interesting parallel on paywalls and access to journalism.
https://news.ycombinator.com/item?id=11592293