Lay off 50 engineers and all the recruiters? Sounds great, except... in a given year, a handful of engineers would be expected to leave anyway from attrition. Either leaving for other opportunities, retiring, or getting fired for various reasons, who knows.

In this case, after a layoff, you can often expect a few more to leave for other jobs because they think it's a bad sign, or they miss their friends, or whatever.

So you probably still want to backfill them. You probably also want flexibility in case you realize one team needs some specific skills you didn't have.

So if you're then expecting to hire 5+ people over the next year, the cost of a full-time recruiter vs a contingent fee of ~25% (+/- some) per hire using a third party recruiter still makes sense.

Source: A quick look at what jobs Meta is still hiring for.