A lot of scientific publishers have hijacked "Open Access" to charge high fees for the same publication as before and pocket more money. For example, "Springer Blood Cancer Journal" charges $ 4,580 as OA fees. I can't imagine how one can rationalize that cost.
* to advance your career you need to publish in certain specific journals
* 5 grand is a reasonable amount of money to advance your career
therefore:
* it is reasonable to pay 5 grands to publish on such a journal
Also, is Nature working on digitizing old content? That can be costly (I remember reading somewhere that it could involve a) finding a library that has a copy and b) flying there to photograph it) and that’s a cost PLOS won’t ever have.
You need to first explain why PLOS ONE is an appropriate baseline. A world class Open Access journal costs roughly $10 per submission [0]. Most arguments I have seen using PLOS ONE as a baseline, talk about the "non profit" part of PLOS. It has to be stressed here at that "non profit" doesn't mean PLOS works on a "non profit" business model. It just means that they generate profit AND the profit isn't distributed to its members, directors or officers [1].
[0] https://gowers.wordpress.com/2016/03/01/discrete-analysis-la...
[1] https://www.law.cornell.edu/wex/non-profit_organizations