After getting tired of constantly searching github and phabricator, I built a small tool that would open git repositories, files, branches, and commits in the browser.

You're pretty spot on about AWS. Storage is super cheap, but data transfer can be really expensive. Also, depending on your users' habits, you'll likely want a CDN to serve your files, especially if you want to serve international markets, and I can tell you that most CDNs are very expensive for video hosting. Third party hosting like Youtube and Vimeo have limits for how you can use them which are easy to go over while full-service video hosting/analytics/monetization like Brightcove and Ooyala will cost you a house.

Shameless self-promotion: you should check us out at dendr.io. We're working on a peer to peer CDN that runs on top of your existing hosting provider (whether you do it yourself, or a CDN) to decrease your costs and give you other benefits. Feel free to email me at "albert@" our domain.