The emphasis on how much a student learns is a red herring.
The schools are charging a premium based on the prestige of the college, the maintenance and cost of running a campus, campus amenities, etc.
When class is online, there are no janitors to pay, no campus cafeteria, no security officers, orders for supplies, etc. What is left? Administrator pay (how many are now needed?), costs associated with teacher staff. Aside from all of this, can someone put a price on the campus experience?
By continuing to charge the same the same rate as before, the schools are up-charging; adding unnecessarily to the student debt crisis.