On auction sites worldwide chinese faked iTunes gift card serials are getting sold for a lot less money than their iTunes value. Currently 200US$ gift cards cost about 3-5US$ in China. In Europe prices vary between 40-60€ per 200US$ gift card.
This issue reveals that Apple seems to have at least one problem: either they don’t have a database of valid gift card keys at all, but is only using checksum algorithms to test for validity of these cards – or their database of valid gift cards has backdoors that have been found by some chinese guys. Although – as always – Apple did not comment on this yet, they are most likely working on this problem.
We strongly recommend to not buy iTunes gift cards currently via auction sites. It is fraud and by knowingly buying those faked codes you are accountable. Moreover technically will Apple block these codes.
Always remember: if it’s too cheap to be true, it is fake.