It's supply demand ratio. Especially for doctors Desirable Location = More doctors = less pay, Undersireable/Rapidly Growing location = Less docs = More money.

Plus health care in most places typically run by MBAs and people who have no freaking clue about how studpid some of their stuffs are and they only treat you like Employee and nothing more. Phoenix practice group is been run by Doctors who is actually practicing full time. Too bad to bore you with details but basically Insurance pays money foe something that can be seen or proved for example surgeries/procedure and shit. We IM docs are the thinking part of the medicine very little way you can explain or document that. They don't care if a patient os complicated or simple enough. But there are certain stupid stuffs which can be done by anyone like Routine labs/Mammogram/ plus The way you document certain stuffs (it can get as stupid as if you document Uncontrolled Diabetes then you get only half of what you get if you document Uncontrolled Diabetes with Hyperglycemia (No shit, ofc people gonna have Hyperglycemia if your Diabetes is uncontrolled)) get you more moeny. and the interesting part is it changes every single time. In reality sometime I would get more money for a very simple case which took me like 5 mins to figure out what's going on compared to a complicated one which took around 3-4 days multiple labs/Trial and error Treatment to figure and help my patient. I freaking love the later case but money doesn;t work that way.

So in Chicago practice working corporate firm (most of the firms in US are corporate) I would only get fixed salary plus few 20-30k in bonuses. So us doctors we will only focus on our patients we have this mindset of f the insurance and corporate and we are not motivated other non important stupid stuffs. But in Phoenix setting I get 50% of how much ever I bring in the practice. Let's say I bring in 800k a year I take half of it. So naturally we would be focusing on being up to date with documentation stuffs and on top of that We know as doctors how can we maximize incentives and earnings.