I'm guessing most of their money comes from businesses who purchase licenses for their developers. I've personally been responsible for four license purchases (my own + 3 companies bought a license for my work computer).
I also had my employer purchase a license. I switched to Atom for a bit, but promptly returned to Sublime
Sublime license follows you around, so new employers don't need to purchase new ones.
Depends on the employer, my big co handles it opaquely so I'd have to get a new one at a new company.
Then you don't own a license, the business does, and they can re-use it for any employee, as long as only one employee gets a license at a time. Their FAQ explains it all well: https://www.sublimetext.com/sales_faq