Totally depends on the area and the type of practice. If you see a lot of medicaid pts, 50-60% of total revenue. If you see a lot of cash paying patients, 60-70% of total revenue. If you see a lot of PPO, somewhere in between. Location also matters. Practices in Utah go a little higher than practices in Kentucky. Practices in LA sell for over 100% of revenue in some cases.
So, the price is all over the place. You can have practices bringing in $300,000 a year go for $150,000. You can have practices bringing in over a million dollars a year selling for over a million dollars. Profit margins can also drive the price up or down. If your profit margins are over 50%, then you bring in a lot more. If they are under 20%, then you will bring in a lot less.
That being said, if you want to buy an existing practice as an investment, then you need to look at the profit margin, what types of procedures are being done, and if you can grow the practice in any way. Then find a practice that fits what you want. Whether you spend $100,000 or $1,000,000 isn't as important as how much money you will make off it.
If you can buy a practice for $100,000 that you can grow and shrink overhead, then that might be a better investment than a practice bringing in $1,000,000 but it costs $800,000 and has overhead over 80%.
Sorry there isn't a more clear answer.