: That has been the business of capitalists since their time in the sun began.
They calculate the exchange value - which is something you presumably are not doing.
: To infer, as you do, that capitalists 'don't really know' what their products are worth---because the customer decides what commodities are worth(!)---is to insult capitalists everywhere.
They dont - they know what they cost by virtue of the exchange values they paid for the inputs - they dont 'know' at what price 1000 units will sell - they estimate that part.