How will hiring more crews and gates be cheaper than one flight getting abnormally delayed? I mean maybe it will be cheaper, but there is no surety about it.

You misunderstand. It's not normal to only have one ground crew, this was a very unusual situation. My guess is a bunch of people called in due to the impending weather, or the airport expected to be shut down sooner than they were.

Like I said, this was an edge case. I've flown once a month for almost three years now and this was the first time I've experienced this.