The buyer value is a concept that is more important to the customers. This refers to the amount that the buyers are expecting out of the purchase of some goods. If I bought a book at a price of $40 then, I loss $10 in the process because as a buyer I expect to pay only $30.
Book value is a key measure that investors use to gauge a stock's valuation. The book value of a company is the total value of the company's assets, minus the company's outstanding liabilities.