Monotype is, by a long shot, the biggest type firm in the world. They own some of the largest distribution platforms (MyFonts, Linotype, FontShop, FontFont) as well as having absorbed many foundries.
Their main competition appears to be large companies which invest in type as a secondary feature, like Google and Adobe—all other font distributors are small time in comparison.
Because of their market share, they are able to set the rules that the rest of the type world has to play by. Prime example: the 50% commission split on MyFonts (a mediocre website the upkeep of which couldn't possibly warrant a 50% fee).
Many type designers have little choice but to sell on MyFonts and similar websites: the alternatives are smaller distributors which are unlikely to make nearly as many sales, or to build a distribution platform of one's own, which can be a huge investment of both time and money.
While sources are scarce, according to this Quora post
(to which none other than @Thomas Phinney
replied), Myfonts made roughly $80 million in revenue from retail fonts in 2013. If we assume that only half of this 80 mil comes from typefaces distributed but not owned by Monotype, and that the 50% fee is universal, they would've pocketed $20 million simply by selling other people's work on their websites.
Of course, Monotype can afford more than any others to advertise their platforms, to ensure that they're always the first to pop up on Google, etc, and thereby ensure that they retain their market share. Essentially, they are big because they are big.
In the meanwhile, Monotype is owned by a private equity firm, who profit from your* labor, by "merit" of having purchased a struggling business in the early 90's for pennies on the dollar.
What I see here is concentration and centralization of capital, which consequently leads to a position in which the distributor is more powerful than the designer, and can therefore set unfair rules.
Am I completely off base? Does Monotype not dominate the market as much as it seems? Do they do good in ways I'm not considering? Is it time for a type union? I'm happy to be proven wrong. I welcome your thoughts either way, as little discussion on this topic seems to exist currently.
*Presuming you sell on MyFonts.
EDIT: As a sidenote, I know I'm coming off rather opinionated here, but I don't really have a dog in this fight as I don't sell on any monotype platform.