Amazon seller selling product for cheaper than shipping cost how???

I have been looking at purchasing some more products wholesale to sell on Amazon FBM but I noticed the shipping cost is more than what some of the sellers are selling some of the products for why is this and do they have shipping prices negotiated with the carriers? I don’t see how these sellers are able to do this when shipping is more than the product is worth and that’s before paying for the product. Any help would be greatly appreciated.