No they do not. For example, every single memory card I got from amazon was fake, even if I explicitly selected "Amazon" as seller. Meanwhile every single card I ordered from Newegg was original and high speed.
I have ordered a few memory cards from Amazon by now in Europe, and I've never had issues with them. I don't think I have ever received a fake item from Amazon. Not where I've noticed it anyway.
I build custom video setups as hobby so I say overall probably I got over 150 cards from Amazon (at least half were fake) and some 100 from Newegg so far (last 3 years) and haven't had a single fake from Newegg. [mostly I use Sandisk and Lennar cards]