What you’re getting at is the government creates these types of monopolies due to massive regulations and licensing.
The issue is not with the college prep companies. It’s with government getting involved in education, making it way more expensive than it should be. The free market will drive prices down, especially in the education market.
What does the government getting involved in education have anything to do with the monopoly power of ETS? MIT is private, ETS's owner is a company. The problem is that MIT accepts only SAT scores - they should be forced to accept other standardized test scores too. That would create an actual market for standardized testing, along with competition and lower prices.
According to the original article, MIT accepts SAT or ACT. I have no idea if SAT is preferred though. It was certainly the default way back when when I was applying to schools.
The issue is not with the college prep companies. It’s with government getting involved in education, making it way more expensive than it should be. The free market will drive prices down, especially in the education market.