In this case Best Buy is simply acting as a marketplace for other sellers. The items aren't sold under the Best Buy name, and it lists who the seller is. They're sold on the Best Buy website, alongside thousands of other sellers and Best Buy directly, just like many other retailers do. Companies like eBay, Amazon, Walmart, etc. all operate marketplace storefronts that third parties use to sell to consumers without having to have their own website and sales infrastructure.