Professors are the producers and consumers of these journals. So, a group of your peers invests time reviewing your work and giving you helpful feedback, and you pay them back by reviewing other people's work.
Basically, it's a zero sum game. So if everybody paid for the reviews they did and then got paid for doing reviews, a lot of money would change hands and everybody would end up with the same amount of money they had to start with.
Of course, the companies that _publish_ the journals take a cut. But that's what it is, a cut. There are really communities of professors participating in a zero sum game.
I beg to differ a little, Professors should be paid to do reviews, and not pay to have reviews done.
The companies that publish the journals don't take a cut, they take the lion's share basically, paying a professor to review would work better in having them take a share of the pie.
But if you pay professors, you either pay them enough to make it worth their time, or you pay them less than that.
In the former case, you are incentivizing people to do reviews who are not actually qualified to do them. Or, incentivizing people to do more reviews than they have time to do a good job on.
Basically, it's a zero sum game. So if everybody paid for the reviews they did and then got paid for doing reviews, a lot of money would change hands and everybody would end up with the same amount of money they had to start with.
Of course, the companies that _publish_ the journals take a cut. But that's what it is, a cut. There are really communities of professors participating in a zero sum game.