Many sellers on Bricklink are honest, however, some are not and WILL shortchange you on parts and WILL overcharge on shipping. They are supported by the admin of Bricklink and there is nothing you can do about except file a case with Paypal to get your money back.
Be warned and be prepared to have to file a case with Paypal every now and then. BrickOwl is a better place and I hope it grows larger. Many of Bricklink sellers are on BrickOwl, hopefully the dishonest ones don't migrate or BrickOwl's admin will take care of both buyers and sellers, and not just sellers like Bricklink.
You have been warned! It is not a matter of if, but when... You will lose some money on occasion and don't bother writing the admin. Just go to Paypal. It will save you a lot of grief. Don't even discuss with the seller, they know that Bricklink won't do anything and will stall you until you cannot file a claim with Paypal.