New York Magazine did a case study 2 years ago. They compared:(1) turbotax, (2) tax attorney, (3) street corner tax service. They made up a fake middle income family.
The results are:
(1) tax attorney charged the largest fee, but their tax return saved the most. Basically their service paid back itself. If the clients were high incomer, the payback would be even more. They know lots of loop-holes.
(2) Turbotax did an amazing job. Its payback was almost as good.
(3) Street corner lady did the worst, making some mistake.