For the most part, scientists publish in the highest prestige journal possible, because that counts the most toward tenure/ pay raises/ grant application chances; the most prestigous journals are -- for historical reasons -- still closed since they are profit centers for big for-profit publishing houses like Wiley.

On the other hand, all the scientists I know wish they could give their papers away for free because it builds their reputation to have people use and cite them, even undergrads at state colleges that can't afford the bigger database subscriptions.

Except for textbooks, scholars almost never make royalties, so the profit incentive isn't what you might think. A scholar makes more money by getting raises from the university, speaking and consulting fees, and publishing undergrad textbooks (sometimes). All of these are increased if their is a wider dissemination of their work.

Finally, .... in the US, almost all research is funded by taxpayers, directly or indirectly, it's just NIH funded stuff that must be free.

Finally, finally .... if it weren't for the fact that the prestigious journals are a ticket to tenure and promotion, there would be no reason to publish anywhere except for Arxiv: so called "peer review", to be honest, is a broken system...