Tell the seller that the increase in the shipping puts the item above your budget and ask for a Mutual Cancellation.
With the introduction of the Global Shipping Program for US sellers, many Canadians are finding that shipping has increased hugely, but at least those charges are stated before the bid is finalized. Theoretically, anyway.
If the seller refuses to open the MC, he can go for an Unpaid Item Dispute. If you have one of these a year, it should not affect you in any way, even if you lose. More than that and you will find a lot of sellers blocking your bids.
But what you describe sounds like an old scam. Refuse to pay the inflated charge.