Well, don't.
Sellers do make mistakes, but we are expected to be grownups about it. EBay requires the seller to ship when the buyer pays the amoun that was advertised.
Occasionally a buyer and seller will agree to upgrade a shipping service (say from regular parcel to Priority Post) for faster delivery, but that is not the case here.
Politely inform the seller that your bid was based on the amount that you can afford, including the advertised shipping. Tell him that if he is not willing to ship for that amount, he should send you a request for Mutual Cancellation.
If he does this,you have choices. You can agree to the MC, the transaction is void, he gets his selling fees back, and you can leave appropriate feedback and the more important Detailed Seller Ratings.
You can ignore the request and after a few days the transaction is void, he gets his selling fees back, and you can leave appropriate feedback and the more important Detailed Seller Ratings.
Or you can refuse the request. He doesn't get his fees back. He cannot open an Unpaid Item Dispute if you do not pay the (original) invoice. And you can still leave appropriate feedback and the more important Detailed Seller Ratings.
If he is smart, he will realize that charging too little for shipping is his mistake and he should accept your payment and ship.
