They don't. The vast majority of my physics knowledge was gained for a few hundred bucks, most of it going to whoever publishes $MAJOR_PHYSICS_TOPIC, by Landau and Lifshitz.
What I paid $30-40k for was certification that I had this knowledge.
We really need to separate certification/credentialing from education. This is the main thing that will allow innovation in education - people need to buy the credential, and since it's bundled with education, they have no choice but to buy unnecessary education.