@PurpleTitan First of all currently the earnings of Oxford and Cambridge business grads are higher than ross business school. Plus London business school probably has most american unis beat in terms of salary.
Also all of your rankings of Michigan are the shanghai international rankings that are completely based off of research. As you can see british schools like imperial, LSE and Manchester outrank Michigan in physics, engineering and econ. Social sciences are rather irrelevant here. If you look at the overall ranking Cambridge is 5 Michigan is like 22.
Michigan spends a lot on research yet produces less citations than universities like UCL and Imperial that get half of the research funds that Michigan has. If anything this proves the university is inefficient. Stanford, Harvard and Princeton spend less on research and have more of an impact than Michigan. The ivies on average spend like $700 million to $900 million which is the range which Oxford and Cambridge are in in terms of research funding.
The reason Oxford and Cambridge have more academic staff is due to the tutorial teaching system they would need to maintain at least a 1 to 4 staff to student ratio. Also if you combine both Oxford and Cambridge to match the student number of Michigan then the £478 million and £371 million add up to £849 million which currently stands as $1.3 billion that is similar to Michigan’s $1.33 billion research income. Oxbridge combined has 41,000 students similar to Michigan and spends a similar amount of money on research.