Welcome to the biggest scam in science. Research funded by the taxpayer, peer reviewed for free by other scientists in a journal run by volunteer editors all to be hosted as a PDF for massive profit by a ‘prestigious’ journal.
At this point, other than being the arbiters of prestige, what do the journals offer that direct peer review does not?
I think the fair value of what Elsevier (say) provide is > $0, but it's interesting to compare with say Spotify or Netflix - who actually have to pay for content.
Speculating: the reason they slap a $50 charge "per paper" for non affiliated access is that they don't actually care about those sales, that's not where their revenue comes from. Essentially that is the "sucker price".