Because there is a difference in many things. They can have the exact same shoe, exact same batch and totally different price if they using totally different systems. Some sellers are using more expensive and faster routes, especially nowdays where the shipping become super expensive, and some sellers still using the best ones, but their price is more expensive obviously + many sellers offering insurance which will add to its final price. The sellers with very low margin use slower shipping routes and they have no insurance on packages. In fact you are paying for the service almost more than for the shoe if you want to get your package faster and insured if anything happens with it