Thomas Sowell is one of many commentators who point out that United States universities will be attractive at EQUAL quality, because they are located in the United States. But indeed, as United States universities attract students from all over the world, that helps even second-tier universities raise the quality of their programs, by gaining diverse groups of students with reasonably strong academic ability.

That's a valid point, and an impressive list - but perhaps they are able to be the best in the world because they are able to charge so much.

That's not always true historically, though. It seems more like a relatively recent phenomenon, but US schools were still the best in the world a century ago. Perhaps it's more accurate that they are able to continue cementing their lead by charging so much.