Agreed. Value, price, and cost are three independent variables. When they line up advantageously, you have a viable product. But one does not determine the others.
Good point. There are actually four variables - one of them is usually money though, so we don't think about it that much. The four are
buyer price (= contracted price + opportunity cost to buyer)
buyer value (what the product is worth to her)
seller cost (cost to create product + opportunity cost to seller)
seller value (value of what he will be receiving in return, usually face value of money)
