1 for 1 isn't worth it, and the UC system already plays that game with international students where one international pays for 3 in-states. Make the buy-in price pay for 10 and I'm in support.
1 for 10 seems reasonable, assuming there is also a strict academic requirement for that privileged student. Even more points if it supports their housing and food plan.
If you fail out Timmy, he has to pay for tuition again thus paying for even more students. Or just charge the 10x upfront + normal tuition/year after that.
Further points if rich kids do household chores, cleaning, cooking etc for less privileged folks. Just strict academic requirement is not sufficient. Rich kids also have to remain in 95 percentile in academics. A further investigation committee need to be setup to investigate every year if rich kids are not using their influence to be among top students in their classes.
You obviously have to balance the legitimate cost against the illegitimate costs people will incur to get kids admitted. I don't know if 3x or 10x is the right value, but it's definitely not "more is better." If you make it cost a billion dollars to legitimately buy your kid into the school, there will still be millionaires utilizing these sorts of bribes.