[yummyfajitas]

There is physical/virtual room, however, the professors may not have the ability to handle all the students.

A single, quality professor is needed to generate content. Content scales.

An army of cheap drones are needed to grade, assuming all grading is done manually. You could probably get a grader for 50 students for $3000-5000 [1]. That's less than $100/student. As long as students pay more than $100/course, online classes will scale.

[1] This is the pay a PTL will receive for teaching a single in-person math course.