You might think they are the same product, but Amazon is currently being overrun by counterfeit goods. It's no better than ebay or craigslist, at this point.
Also delivery timescales vary a lot. The worst are the ones claiming to ship from local warehouses and four weeks later you get an envelope from China. Basically they just con you on the wait period. But hey you can always go to a local shop and pay £20 for 16GB microSD card or USB cable.