I have products that are supplied from approx 10 different suppliers and prices fluctuate widely. For me, the purchase price of the product should be the weighted average of the purchase prices for all quantities of a product that I have received. So as a PO is marked as received, the purchase price for each received product is adjusted so that the purchase price = weighted average purchase price given the quantity already in stock vs the quantity being received.
Since the products themselves are indistinguishable, this better reflects the cost of the stock that I am holding. If I were to use the latest price, it might considerably overstate or understate the amount paid for the stock already on hand.
To be clear, holding multiple versions of the product at different purchase prices (Multi-inventory add-on) doesn't meet this need because the sales price cannot be easily set to a profitable level without knowing the average purchase price of the products.