Yes
This has been known to economists for a long time
Medicine generally has had its progress (as a general good) held back by misaligned incentives for a long time
See "neglected tropical diseases"
As true in psychiatry as anything else
That seems totally different than what the OP is trying to imply, which seems to be that people who worked on the DSM added illnesses to it so they or their backers could financially benefit. If it's just a matter of "illness that can be better monetized have more financial backers, and therefore they get more attention", that seems... fine? In an ideal world I'd want malaria and whatever first world ailment (obesity?) to be treated equally on some objective factor like QALYs or whatever, but I don't see anything intrinsically wrong with private companies preferentially funding research that they stand to benefit from.
Wouldn't we expect it to be more true the fewer objective measures there are? Like if a treatment is supposed to improve blood sugar, and we can measure blood sugar cheaply in real time... we should expect misaligned incentives to have diminished effect compared to something where there is less ability to objectively measure, such as pretty much anything in psychiatry.
If there is money to be made the medical establishment will put much more effort into that area than if there is not
Bringing it back to the DSM: The more human states of mind that can be classified as a "psychiatric illness" the more money there is to be made in marketing various therapies
This is glaringly obvious in drug development but it applies to all forms of therapy that can be done in a way with a gate keeper who can charge a toll
Like, we can't sell treatment's for people's sixth thumbs because virtually no people have a sixth thumb and it's unambiguous that they don't-- and even among any who do it'll probably be clear if it needs treating or not. But I can sell a treatment for your hyper-meta-ego because who is to say if a person has one of those or not or if my treatment of it is successful or not?