: They calculate the exchange value - which is something you presumably are not doing.
Now that you're BEGINNING to grasp the idea of exchange-value---after SDF and RD have so patiently explained it you---you seem to think that you can use it as a weapon to obfuscate the simple idea that capitalists DO have prety solid notions of what rates of exchange to expect.
Of course there are crises of overproduction and stock-market bubbles---but generally capitalists know that constant + variable IS their 'overhead' and that paying labor LESS than what it actually produces will create surplus.
You wish to infer that they're running in the dark, tailing the customer.
And that's nonsense.
That candy-bar is NOT worth $100 when some isolated crank buys it at that price.