Even if it costs nothing, Facebook is a far better option for hair salons and other similar small businesses. Facebook drives engagement and views, while nobody will bother with a self hosted website. The oft repeated lesson here is that convenience trumps privacy for the vast majority of users. If you look at the last decade, in spite of there being robust, self-hosted solutions for syndication and engagement such as RSS, pingbacks, OPML etc, in the end closed systems won.
Maybe there is a secret ingredient to making it work again, but we don't know what that is. Yet.
I think the secret sauce may be in things like 'call ahead seating' or 'get in line, online' that some restaurants and hair styling places do now. You don't typical get that capability on facebook, and it's a differentiator.
Thing is, why would a hair salon (which presumably has no advanced technical skills) choose to write or purchase software to run on their FaaS service, instead of simply registering an account on a SaaS service that takes care of everything for them, and even integrates with FB?
Maybe there is a secret ingredient to making it work again, but we don't know what that is. Yet.