The kinds of bills that some large company development environments end up running are surprisingly high, but those companies also think the opportunity cost of losing productivity on application team developers to also very high. That's how you find companies that decide to hire very expensive teams to, say, add types to a dynamic language, rewrite a standard library, invest in massive parallelism to run thousands of CPU hour integration tests in 15 minutes, or many other projects like that which no normal company would ever consider. If it gets some project team to cut delivery times by 3 weeks, it's all considered worthwhile.
Where we run into trouble is when we try to copy the shape of those big companies, and the kind of initiatives they fund, into startups, or mid-range companies. In quite a few ways, those top companies are better at development, but the base costs are only worthwhile if you have a money fountain of real revenue that grows far faster than your dev expenses. Trying to copy them with very different conditions is going to lead to tough problems, possibly company killing, and it's the kind of imitation we see all over the industry.
So yes, someone like Github is going to have eye popping expenses, because the alternatives to avoid those expenses just don't make sense to them. If you are not working in a multi billion dollar company, their practices can be interesting, but it makes as much sense to emulate them as it'd make for you to hire an entire Formula 1 pit crew to keep your commuter car in good shape.