We operate a dozen of our own colos, with a virtual colo on AWS for insta-scalable multi-region redundancy, and an Amazon "colo" costs the same as about eight of our own when spun up and serving at least a gigabit of traffic.
However, the difference is less if you're going from zero sys admins to 24/7 says admins. I'd SWAG the crossover is once your AWS budget exceeds 4 full time sys admins willing to do shift work.
Being a forum where low wage/students/anti-corporate/anti-advertising types go and share memes is the elephant in the room problem.
For example, I wouldn't be surprised if the Internet's largest right-wing community turned out to be one of the subreddits.