I don't know about psychiatrists. I know that in some medical specialties, part time is 40 hrs per week!
Psychiatrists on average make about 150-180K a year. I know some that make a million, some that make 130K.
While psychiatry may make more money you're also likely going to be have a huge debt burden and be forced to work crazy hours (80+) for a few years.
By the time you graduate residency, working 40 hours a week is pretty much nothing--at least it is for me and most medical doctors I know.
There are ways to make very very good money in the field. Several areas of the country are extremely underserved and if you set up practice in one of those areas you could make very good money, among several other options, but I've noticed that the majority of psychiatrists just take a job and don't think of creative ways to make a lot of money. I think it's a combination of being in a 6 figure salary comfort zone so why take risks?, the other factor being that medschool in general kills off creativity in the brain, and that some of those ways to make money aren't exactly ethical. E.g. running a Methadone clinic where you know more than half the patients are just selling their Methadone to someone else.