This is part of the reason why I decided not to apply for law school despite scoring well on the LSAT (176). I couldn't commit to working 80 hours a week at a big law firm to pay off 250K of debt unless I was sure I loved the work.
It would be interesting to have some kind of exam showing equivalent knowledge, but I haven't seen attempts in that direction that aren't worse assessments than the degree/GPA. For example, as weird as law-school is, the bar exam is even weirder (deliberately so), and generally a terrible model to follow.