I can think of a few more points-

Cranbrook has very small class sizes and a very supportive environment compared to even other privates and definitely compared to publics. I know of people who struggled in public school and thrived at Cranbrook. Cranbrook allowed these students to fulfill their potential as opposed to the more "sink or swim" environment in public schools.

If, however, your kid is thriving in a public school, I would not send to Cranbrook, even if money were no object. I don't think there will be any disadvantage in terms of college admissions were a student to attend Bloomfield or Seaholm. They do about as well in terms of sending kids to the Ivies and the like.