Both theories use the SAME formula.
Final Price = Raw Materials + Labor + Overhead + Profit
The difference is that Marx pushed that labor is what makes a thing have value. Wheres Musk pushes that humans have 0 value, and should be removed whereever possible.
Same thing, different conclusion.
And know what happens when we get "perfect idiot index" of 1.0? There are no workers, no money, and wealth is accmulated purely in the hands of the elite. Hell, even Ford saw this in tge early 1900's - who'd buy cars if nobody can afford them?
There are very very simple proofs to invalidate the LTV, for example the fact that two items requiring identical amounts of socially necessary labor can have very different prices. In my experience, I have only met one person who earnestly believed it (an old college classmate) and his basis was self-admittedly purely ideological. In the end, I think the most elegant way to think about it is to reverse the causal arrow. Labor does not create value; perceived value decides which labor was worth doing.