If you work as private practice (whether solo or part of a smaller group and you have the connections to collect all billings yourself and not funnel any revenue to administrators), then the revenue is all based upon the volume you have. These practices are called "99213 mills" because of the CPT billing code for for Level 3 office visit. While some visits will be very straightforward and a level 1 or 2, a few will be level 4. just "average" it as 99213.
99213 usually pays about $100 give or take in NYC (for Medicare and the Managed Medicares/Medicaids. Commercial insurance will allow that much but may not pay at all depending on the patient's deductible and out of pocket max situation). Depending on the insurances, copay or coinsurance is a percentage of this (meaning patient pays that amount and the insurance pays the difference)
You can do some ancillary things liek smoking cessation, alcohol cessation counseling, vital sign, 12 lead ECG etc... but let's just keep it simple.
20 patients x $100 per day - $2000 revenue.
If you worked just 5x a week x 50 weeks (let's factor in some vacation and holidays)_ - then $2000 x 250 = 500,000.
Not everyone can launch into solo private practice and get the patient volume like that. unless you have connections to an IPA or some other group of physicians who have collective bargaining power with the insurances, don't expect to walk into a job and print money.