Yes, taking 1x sales, 12x earnings, and tangible book value and averaging these is the foolproof way to come to a valuation for a company. That's what you learn in finance school.
Honestly the author may have made some other good points, but he completely lost his credibility with the 1st paragraph. Nobody should be selling after reading this.
This is direct from Guardian. They wrote it, this is a cut and paste of it.
Sorry, Gotham, not Guardian.