The company is very small, and they're doing a lot with what they have. Steam alone is full of arcane features that I keep discovering. There's a lot of backend stuff. They're making games and hardware.
Perhaps some of this is contracted, similar to the Linux compat and drivers, but it's still impressive to me, compared to the orgs like Spotify, order of magnitude larger with barely any features at all. (I understand there's legal, huge backend, and I didn't see many bugs over time, but still)
The number of developers needs to grow log(n) to the number of users to handle all error reports. Valve is way under the log(n) of user.
The company makes $50,000,000 for every employee each year. It can afford more employees.