You said the rubber seals, the custom of the price, it depends on what you said is where the different parts of the seal, that price is not the same, on the outside of your custom must be more than 4S much cheaper.
This custom seal is not to say that there is a fixed price, are generally non standard parts, are according to the requirements of customers, pricing, because the number of different customer material, size and other aspects are not the same, decided to seal the price is not the same.