At CMU, annual tuition is less than $24,000. There are less than 14,000 students enrolled, which means total tuition paid must be less than $336M.

If all that money were equally divided between the 1400 faculty members, they'd each get a salary of at most $240k per year, which is really high in the grand scheme of things but kind of low for these specific facebook jobs that we're talking about.

Now consider that much (most?) of that revenue must actually be spent on the 2,500 staff members supporting university operations, building maintenence, etc.

I don't think there is any great mystery to solve here.

Edit: see the replies to this post. It seems the tuition at CMU I'd double what I thought it was. I still don't think the revised numbers are any more mysterious, though.