AWS is always more expensive than owned hardware + good team -- it's after all what they generate their profits from. However, it's also probable that they were

AWS is always more expensive than owned hardware + good team -- it's after all what they generate their profits from. However, it's also probable that they were using the cloud wrong. Their software (afaik) is a typical 3-tier application coded on Ruby on Rails, which probably implies that they used just EC2s, with probably an orchestrator on top. Also, if they didn't need any new staff after moving to their own server rooms, this implies that either their staff was having lots of free time or that their staff currently is overworked.