I don't know why you say that 40% or whatever percent of his business is lost FOREVER...

If, as I suspect, he loses his business, that is forever.

I don't see him replacing his customers. Afterall all the people left in the area already have their barber. There will not be in influx of new people anytime soon. Actually companies are relocating to other localities for the foreseeable future.

The business is lost.