AI tools are often sold on a headline monthly price that looks easy to justify. For a firm of two to twenty fee earners, the real cost and return of legal AI are broader than the licence, and worth working out before a partner signs.
What it costs
Count the licence per user, then add the parts that are easy to forget. Someone has to choose the tool, set it up, write the policy and train the staff. There is a learning period where work runs slower, not faster. And there is the cost of checking output, which never goes away. A tool that is cheap to licence and expensive to supervise can cost more than it saves.
What it returns
The return shows up in time. First drafts of routine letters and documents come back in minutes. Research that meant an afternoon can take an hour, provided every source is checked. Reviewing a long bundle for specific points is quicker. The gain is real, but it lands as reclaimed hours rather than a line on an invoice, so measure it that way, in time saved per fee earner per week against the all-in cost.
Start small and prove it
Rather than a firm-wide commitment, begin with one tool, one team and one task where time is clearly lost. Measure the hours before and after. If the saving is real, widen it. If it is not, you have spent little finding out.
AI earns its place in a small firm when the time it gives back outweighs the time it takes to run safely. That is a question of evidence, and it is answerable.
The SRA's research on AI in the legal market is a useful check on the vendors' arithmetic.
If you want this arithmetic done for your own firm rather than in general, the readiness audit does exactly that sum: see the packages.