The Tesla stock price is based off of the cult-of-personality followers of the CEO and his promises that FSD, Cybertruck and Tesla Semi are _just around the corner_
The latter two are just a matter of mass production, intentionally delayed in favor of other priorities. FSD is certainly possible, and good headway is being made on it. When it’ll be as good as a human however is an unresolved matter setting aside the hype and speculation.
Nothing is ever just a matter of mass production. Scaling brings its own, massive problems, some of which Tesla experienced with the relatively simple Model 3.
You're right, scaling is another topic. If you can produce 5 prototypes you can produce 500 of them. Making that happen at scale in a timely manner requires introduction of automation, assembly lines, humans, checks and so forth. However, I argue beyond being laborious it's not any sort of impossibility as compared to something like FSD.
"A matter of mass production" is like saying step 1 draw a circle, step 2 draw the rest of the owl.
The factory is the hard part of car design.
The Cybertruck only recently had the design finished ..