The reason medical schools cap the number of entrants is the same reason they raise tuition exponentially - it's expensive to run a medical school. It has nothing to do with the number of applicants.

Also, 25 hours per week? My wife is a physician. Nobody at her hospital works less than 60. Most work 80 or more. Surgeons are close to 100. For many full time primary care physicians, it works out to about $10 / hour when first starting out.