Average Pretax Margin: 10.5%
Small fry may have difficulty raising the scratch to buy expensive equipment; once it's installed, though, economies of scale start to kick in. Depending on the type of lab, the marginal cost of doing "one more" test--thanks to typically lean staffing--can be very small.
4. Investment Advice
Average Pretax Margin: 11%
These are financial planners who don't have the authority to execute trades. Few things are as opaque as fees for financial-services fees--which is probably why this industry makes our list.