The minimum level of functionality required is to show how much it costs to buy a card. After that, I can see how it would be important for sellers to be able to show how bulk orders can lower the cost of shipping. There are ways both concerns can be met, but the first is most important. The way it is now creates incentive to list free or low shipping, then raise it in the checkout page.
That being said, I have to retract the statement "It's not just a few sellers either, it's like every seller." I did a wider range of searches and it's not as prevalent as I initially thought. Any listing with $0 shipping is pretty much guaranteed NOT to have free shipping, but the majority of postings seem to have legitimate costs. Once you learn that "rule" It's not so bad, but it's still a problem, because when it happens to the buyer it's frustrating and drives them away, and other sellers are overlooked due to their apparent higher shipping.