All the door panel kits I've done so far were warranty so I don't know the price BUT I'm sure that they're not cheap as they're complete panels (never cheap with any car). Your dealers parts dept should be able to give you a price and you can do it yourself too (easy), but they come only as a "kit" of two panels to my knowledge as that's how we always get them and replace the other side panel too even if it's still OK at the time.

The only thing that you won't like about the "kit" is that if and when you replace the LF panel, you have to cut out the hole for the remote mirror switch as that's not done for you (oddly too), but it's at least marked on the inside. Maybe in other countries they don't have remote mirrors?