>>281708530
It's fairly obvious if you can count.
The wage for mangaka is usually from 7,000 yen to 10,000 yen per page, dependent on magazine. In addtition they get royalties from volume sales, 10 percent of printed volumes (they get everything at once though, so if 3000 volumes are printed, they get money from all printed volumes, not only those sold), and 15 percent of digital volume sales sold. For monthly mangaka, the royalties is usually a pretty measly sum.
So the wage for a mangaka with like a 20 page series a month is then 200,000 yen, which is equivalent to about $1360. Yes renting in Japan is cheaper than in a lot of the rest of the western world, but not that cheap. You can't expect someone to live of $1360 a month.
How people can't figure out something as simple as this is beyond me.
Also this manga sells about 2500 volumes physically, and extrapolated about 3750 volumes digitally. A volume is 770 yen. So
2500 x 770 x 10 percent = 192,500 yen (hard to say what the artist get since the artists get for volumes printed, not volumes sold)
3750 x 770 x 15 percent = 433,125 yen
Total 625,625 yen per volume, which is equivalent to about $4260 (a little higher most likely since she gets money for printed volumes. With a volume about every six months or so, usually there's a break when they release a volume that month, it's not a lot of money mangaka's make on their job, and not certainly enough to make a living for a monthly series