I'm fairly sure that $30k figure was a reference to the per-student tuition rather than the professor's pay. :=)
Professors make much more than $30K. Depending on their rank they may go as high as $250K...and that is for teaching a couple classes several months a year usually with teaching assistants and research assistants). Those with tenure get a year off with 1/2 pay every seventh year. It is a rough life, no?