I would argue that VRM already exists to some extent. When I want to buy something, I Google it. You can instantly comparison shop and add items to a shopping

I would argue that VRM already exists to some extent. When I want to buy something, I Google it. You can instantly comparison shop and add items to a shopping list to keep an eye on the price over time. You might not directly negotiate with vendor's, but I am not sure most people really want to or need to, including HN'ers.