[autocorr]

This is a little surprising since MNRAS's niche has been that it had no page charges. So if one was short on grant money then you went with monthly notices. That's pretty nice if (a) you have zero grant funding available or (b) want to prioritize conference travel for students/postdocs.

MNRAS is one of the three "main" journals for astronomy along with Astronomy and Astrophysics (A&A) and the Astrophysical Journal (ApJ and AJ). A&A is mainly Europe and ApJ is more mixed but with more North America. Along with Nature and Science for high-impact things and regional journals for Japan, Australia, and the US (PASP).

[aragilar]

I think it's due to Plan S, see https://telescoper.wordpress.com/?s=plan+s.