30k or even more if you hardcore 24/7, i never did it myself because i am not robot xD
but pretty sure i make around at least 10k per month farming casually in mirror and INTER.
Just wanna add some note.
Aside from producing/farming things, you also need to sell it, thus rivalry on EM is another parameter to consider.
With that in mind, rpk-ing ingame is another strategy to delete your rival productivity. Cause everything is a competition, even we live in a world full of competition to bring food to our table.
Soo whoever say rpk is useless and there must be none, i believe they live in a world full of peace without competition eating grass everyday xD