Purchase Price set on Purchase Order, when a preferred vendor price is already set on item

I have a Non Inventory Item for Resale with multi subsidiary vendors. Both the US and UK vendors are same and are set as preferred vendors. The vendor price set for both preferred vendors is also in British Pound(British Pound : 175). And the purchase price on the item is set to a different amount(124). When a Purchase Order was created for US subsidiary, the preferred price was set on item. Now, when I try to replicate the issue, the preferred vendor price is set.

I could not find any script or configuration that is setting the price to the purchase price of the item. All documents I read, specified that preferred vendor price is given preference over purchase price. Can you please help me identify the reason why the purchase price was set on the purchase order?