[davorak]

> The point is that the cost of the college grad is not a basis for economic decision making.

The common assumption that ajmurmann and vasiliys are likely working form is that value has been retained during the ~20 years of investment and the cost is proportional to the value and there cost is a reasonable proxy for value.

It is an assumption that does not always hold, but is common enough to do as a first order approximation.