Hi... there is no wrong for a buyer to ask a seller if they are willing to sell the item at the price the buyer is willing to pay.
Those buyers have already did there homework and know what the prices are going for by doing a "Completed Listing" search on a item.
So type in the item in the search bar at the top of any ebay page then on the left hand side of the page click on "Completed Listings" the ones that are in green is the ones that sold.