At the end of the day, it certainly didn’t hurt to have a tutor and highly likely that it helped D20 stay on the studying/prep track (e.g. having a coach/mentor throughout the process who works with many high school students, knows the most effective study techniques, etc.).
While she didn’t continuously use the tutor for 9 months, I would say we spent about $2,500 on test prep. Also, spent another $3,000 for a private college counselor over two years who helped D get into her top college. Money well spent IMO. You get one shot at an undergrad degree, why not give it 100% if you have the means…