Truth value

i mean, the truth value of a product, a service.

for a product, the truth value may be the (Price - profit) by the retailer.
let say a nike runner, it sell for 100 to a customer, and the profit is 20, so the truth pric is 80.
what this 80 contain? it contains the material price(rubber, cotton,etc), the factory profit, labour wage, transpotation. well, it seem to be able to calculate, but it si not, how to calculate the truth value of labour wage? and also, how to calucalue the truth value of the material price?

depart from those truth price, hwo about the truth price of a service... how to measure?

for most people, the price of a goods is defined from discussion between seller and buyer. yes, this is the market price. not the truth price.

the truth price is somekind of value, absolutly defined the value of a goods or a service, which independ of the location, time or currency but the product itself.

for anexample, the truth value of being an engineer is equal for any engineer (i mean the same kind of engineer in same post, equal among of work), however, the market price of each engineer may be different, because of the company, the socialty, the econmonic power, the demand and supply.