In looking at the cost of privates, and comparing to in-state public costs, I look for a certain break even point on the cost of attendance (tuition, room and board). I don't throw in every other possible cost as these are variable such as books, insurance, fees, travel, personal, etc....
In my state, there is a range for in-state costs for tuition, room, and board. But the range is somewhere between $13,000 per year for the least expensive public schools to right at $19,500 per year for the most expensive. A typical private may run from $32,000 up to $40,000 per year for tuition, room and board.
So, what do I mean by breaking even on a private school? If your kid can attend a private that he or she wants to attend, for the same costs as the most expensive in-state public that he or she could gain admittance to, then that is breaking even. This is my terminology, slant or justification. Regardless if the kid is an athlete or just wants to go to a smaller, private school as a student.
So, if you're kid can gain admittance to the public that costs $19,500 per year but wants to attend the private that costs 39,500 per year, then the kid will hopefully receive $20,000 in a combination of either athletic scholarships, institutional scholarships, outside scholarships, need base funds, or financial aid.
This is just my quick and dirty formula in looking at costs. Has nothing to do with the reputation of the schools, programs offered, or quality of instruction.