[gavazzy]

Arxiv is by its nature open access; Arxiv does not charge for access.

On the other hand, the articles that this site hosts require payment to access. The journals typically charge $30 / article, or roughly $2,000 / year subscription.

Note that for both the open access or paid journals, researchers do NOT receive any compensation when users download articles. That is, despite the research being mostly paid by taxpayers, a PRIVATE company receives compensation for the work done by the researchers. Not only that, but the researchers have to PAY a publication fee, and that fee is higher if they want to allow open-access.

[qft]

Not only the researchers do not receive any compensation, they actually need to PAY the publishers hundreds of dollars minimum to get their work published.

[max_]

How come all papers i have come across at the arXiv are readily downloadable as PDF?

[Blahah]

Because the arxiv is a place that hosts free pre-prints. By contrast, sci-hub is a way to get normally expensive articles for free. Arxiv stuff is already free.