As a customer, you will be able to see the product with least price in the shop page of the store. Thus if Vendor X has a product of $50 and Vendor Y adds that product to his store with price as $40, then in the shop page the product with least price ( i.e that of Vendor Y) will be displayed.
In addition, in the single product page, all other additional products will be displayed under “More Info” section as shown below: