I don't have evidence Reddit would reduce operating costs since they haven't switched yet, and I don't have access to their code/architecture/etc to decide one way or the other. However, based on my personal experience, static type languages are much faster than dynamic languages and use much less resources. They used substantial less servers to maintain the same SLA throughput. You don't have to take this advice and keep paying for the high cost of hardware. There's a belief that developer cost is much higher than hardware cost and thus it's justified. However, when scaling out, hardware cost is much higher than developer cost. Developer cost is a fixed sunken cost at initial development. Afterward it's just maintenance and can be scaled down, but the hardware operation cost is ongoing, increasing years after years.
Proof that in this single instance, Reddit developers decided this was a suitable optimization for their codebase.
This also calls into question the original assumption, that posters believed Reddit had far too many wasteful servers to handle their service, and that it was because they use a dynamic language.
