[ghaff]

>I've heard a bad hire costs $X, where X is some surprisingly high number, but why must it be this way?

Because most companies don't (and generally shouldn't) operate like pro football teams. "You've had a couple bad games; we're cutting you. Sorry it's just business." Most (though of course not all) people think that once you've hired someone, you should really try to make things work. Both because of the costs associated with someone getting up to speed at a company and because of the personal cost to the person being fired. Different companies have different philosophies of course.

[acjohnson55]

I think there are humane ways to part ways with an employee who just didn't work out. Give generous severance and some warm intros to places that might be a better fit.

If you really screwed up, make that choice soon. In the more common borderline case, that person is still giving you decent value, so it's not a total loss, even if you invest effort in trying to coach them up to your high bar.

[jimhi]

I like the sentiment, but I would rather a potential hire just apply cold than if a company told me to look at a candidate they just let go (even if it was google).

Warm intros from an entity that just rejected you would be a terrible signal.