Earlier quoted context omitted.
What you see as a problem, I see as a positive. This is clearly an edge case - it's not the norm by far. The norm is that sellers make darn sure that their product is "as advertised" so that they've set the expectations correctly. This results in higher feedback for the seller. Sure, you have some slime ball sellers there who say, "Give me 5 stars!" but that, again, is not the norm.
And, in the case of this seller, it appears this was not an isolated incident. In their reply to the one star review, they state: Sorry- no idea there was postage due. This has happened alot from USPS lately. http://feedback.ebay.com/ws/eBayISAPI.dll?ViewFeedback2&...
Does this really happen? You take the package to the post office, they weigh the package, charge you money, give you a receipt, and then later demand money from the recipient in order to finally deliver the package?