Oxbridge funding

A couple of weeks ago it was announced that the Saudi defence minister has donated £2m to Oxford University "to expedite the application process" and "to identify four to six colleges with resources and expertise" for visiting students from Prince Sultan University in Riyadh.
Cambridge University is in the process of raising £1bn. Why doesn't it consider holding a one-off sealed bid auction for a certain number of graduate places? I'm sure many international companies would leap at the chance of buying research opportunities at one of our finest scientific institutions and that the £1bn would be raised pretty swiftly.