I do not think that we ever figured this out. “College cost inflation” might have been what might have been fair, but our youngest ended up under-spending the college budget by quite a bit (and continues to do so with a funded PhD program).
I guess with multiple kids you just try to be fair, and understand that the definition of “fair” will never be precise.
Our oldest also attended a university that was only affordable due to a merit based scholarship, and needed to maintain a 3.0 to maintain the scholarship past the first year. We never figured out what we would have done if she did not maintain the scholarship. Fortunately this never came up. In retrospect I do not know whether we should have figured this out, or if it was just as well to let it slide.
I continue to wonder whether Solomon had children, or if he figured out that even he was not smart enough to get this right.