I can't speak for psychiatric drug trials, but I have a close friend who is employed by a group of cardiologists (she's a pharmacist).
This group does interventional cardiology...so they have lots and lots of drug trials available to them.
They get paid enough to have their own pharmacist & nurse who does just drug study work on their patients - no other office stuff. The paperwork is overwhelming with drug trials & the time required can be immense. That is why the nurse is there - she draws all the blood samples at all the strange times (often these pts are hospitalized & get blood draws at odd hours...since the trial is not hospital run, the hospital staff doesn't draw the blood - the physcian's drug study nurse does it). The pharmacist obtains the medication, tracks the dosing, obtains data & documents it & often submits the raw data to the individual who actually writes up the results to submit back to the company. The pharmacist also has to keep track of all adverse effects both during & after the study has completed.
I don't know how much the physician himself (or herself - there is a woman in the group) gets personally.....the group is paid an amount for being a site for the study & they get paid for each participant who is enrolled. But...its enough to pay these two people. The physicians do bill for whatever they might just as they would any other patient.
In my area - SF - there is a large company which just runs drug trials. They do everything from statins, to smoking cessation adjuvants, to cardiovascular drugs, to hormone replacement therapy......Their base staff is composed of a CEO (who is a physician), a CFO (who is not), about 4 other physicians, a number of nurses, a pharmacist & one person who is devoted to just grant/drug study writing. They hire physicians as needed depending on the study. It would be interesting work, for sure.
It really is an expensive process & hard to take on solo....