Pablosnazzy,
Every expense that you mention in your #28 post is shared by the online warehouse.
However, you also must consider that they have to maintain a huge inventory of stuff, maintain a computer catalog with ever changing sales and prices, Their warehouses need equipment to move stuff around and their employees get benefits. They pay workers comp and other insurances. They have to absorb damages and returns.
All this on a much grander scale than the Mom and Pop down the block. If something comes in damaged mom and pop notes it and it gets returned. If a warehouse employee damages some stuff and no one knows about it, tough luck. They have to eat it.
By the way, I don't think asking a vendor if they can sharpen their pencil is getting in their face.
They may even be happy to move some older inventory to make way for the new.