I can’t recall there being fake replicas of Ledger Nanos S (I do recall an article on Fake Trezor Ones: https://blog.trezor.io/psa-non-genuine-trezor-devices-979b64e359a7). That does not mean it can’t happen, especially if the market on a bull run, and that is why it is essential, as you say, to purchase the devices on the official seller’s site (they will list official resellers if need be).

What we have seen are sites that allegedly sell Ledgers in bulk for a very low price (you’ll probably receive nothing at all there) and people that sell a preconfigured Ledger (as is described in the 34K$ case).