Jack-of-Diamonds

Regarding expecting shipped cigars at the advertised price:
I realize there is a glaring difference in purchase price and their real price on this one. But suppose it weren't so glaring. Say you order a box of fine old-world cigars at a reasonable price. The vendor ships them, but then tells you you owe them more money because the price they showed on their website, accepted the order at, and shipped at, was not their real price. What then?

Thanks! Don't mean to sound like a nutjob on my first OP. I am really torn on this one between the practice and ethics on both sides of the deal.