Some large groups self-insure, so there are no "premiums" but the pool is funded through general revenue. Now how directly that money comes out of your pocket depends largely on how you are paid. Are you salaried by the group? Do you get a production bonus? Do you profit share? Are you a partner and take home whatever is left after the bills are paid? And then of course you factor in Catalystik's point of risk and how many claims you've had. It's hard to generalize.
In the end, you have to make enough money to cover your overhead, including what it costs to insure you. Except for a few high-litigation risk specialties, most docs have no problem doing this and still bringing home six figures.