Ice cream is being priced too high if the ice cream sellers would make more money by decreasing the price of ice cream. If they wouldn't, it is appropriately priced.

Or, from the buyer's perspective, it is priced appropriately if the total amount buyers would spend on it would go down if the price is lowered or raised.

There isn't a correct intrinsic price that an object should be sold at that can be calculated based on the ingredients and labor. That idea is one of the fundamental flaws of Marxism. Price is a compromise between the buyers and sellers, based on the values of each.