Firm foundation theory isn't really a theory. There's actual math.
Let's say you've got $40. We're going to buy a 6-year CD at 2.25%. After 6 years you've got $40.91.
Let's say instead that you've got a $40 share of GM. It varies, obviously, but for the sake of easy math let's go with that number. GM has paid a 38 cent dividend the past four quarters; at the end of six years (assuming GM stock hasn't gone up) you've got $49.12. The "intrinsic value" of GM stock over 6 years in this case would be $48.21.
Obviously you can get a lot more mathful but basically, the "fundamental value" of an equity is what it earns you above and beyond a "risk-free" investment. Thing is, "firm foundation theory" tends to reward stocks that, you know, actually fucking pay you so it's seriously out of favor in this land of 350:1 P/E ratios and negative goddamn dividends. The "fundamental value" of Tesla stock is well below what it costs you.
But I fuckin' own some.