I don't think building purchasing should even be allowed, remove all of the slippery slope and put students on equal footing.
If that rich family didn't end up having a kid that needed to get into that school then the building would never be built - but the family is certainly able to afford funding the construction of that building. I think that's unfair in it's own way on all parties involved.
Thanks to the current tax environment the school doesn't have some alternate choice; the state is not going to step in and provide that funding.
As an administrator do you take the money or do you skip out on expanding a department or admitting 20 kids who need a full ride scholarship to attend?
(not saying I agree, just that there is more utility)