This is a matter of wht principle used for product cost. With setting Standard cost the deviation between the cost on the product and the purchase price will be posted to a price different account, and be reported to P&L (Profit & Loss) on goods receipt.  Stock will still be valuated on the balnce sheet at the standard price set on the product. 

The recommendation is to use AVCO or FIFO costing. Then the stock will be evaluated to actual purchase price, and for the P&L it will be reported as COGS (Cost of goods sold). It will be more correct for Gross Marging report. 

Another disadvantage with Standard cost is that the cost is not fixed forever. Over time, prices will change. Businesses that use Standard cost a principle must regulary modify the cost.  Usually an activity at year end closing.

In V14 the product cost is posted from goods receipt at the price on the purchase order.  In V16 they made an improvement that the product cost will be adjusted if the price is different on the vendor bill.