Matching the cost of a genuine context switch should be a (laughably bad) upper bound for any language's particular concurrency offerings. It is not reasonable.
Reasonableness is relative and use case dependent. The post itself illustrates how the cost is insignificant compared to other "wasteful" operations related to CSS handling.
If this is too much overhead for your use case, there are plenty of other approaches and languages to choose from.
If you're not any better, just replace your whole hosted concurrency system with a statement that triggers sched_yield.