So the ADA has some data which we will still take with a grain of salt but it's a start.
https://www.ada.org/~/media/ADA/Science and Research/HPI/Files/HPIData_SDPI_2016.xlsx?la=en
Table 13: Practice Expenses per Dentist (Excluding Shareholder Salaries) for Owner Dentists in Private Practice, 2016
-based on 506 responses the median practice expenses for a solo GP = 380,000
Table 5: Gross Billings Per Dentist for Owner Dentists in Private Practice, 2016
-based on 553 responses the median billings for solo GP = 620,000
That works out to a 61.3% overhead.
Things to be aware of:
1. The overall response rate was 14% (im assuming this was both gp and specialist)
2. The survey was sent to 11,160 GP
3. Numbers were self-reported
4. All the pertinent numbers move around:
I think simple math with the billings and expenses above give you an approximate
lower bound of a value I'll call net-benefit to the owner.
But, did the owners report billings as adjusted production? collections?
Do the owners count their car loan, phone bill, CE expenses etc as part of practice expenses?
Is the payment on the practice loan and/or building loan included as practice expenses?
To be sure they are expenses in the sense that your take-home is lower but also
you're gaining equity if you own the building and definitely by owning the practice.
Did the owners' accountant try and include as many expenses as possible so that less
income gets reported for tax purposes?