It's foolish of the seller to refuse to send a Mutual Cancellation Request to a buyer who:
a) Didn't read the listing, including the shipping cost,which is posted before the bidder confirms his bid
b) Won't pay.
On the other hand, if you do not pay for the item you bid on, you will have an Unpaid Item Strike against your buyer account, and most sellers have automatic Blocks against bidders with Strikes, making it more difficult for you ever to bid on eBay again.