The Ledger co-founder has posted on reddit many times that it is not recommended to buy Ledger products from third-party merchants that are not part of the official reseller network. They are not saying you shouldn't purchase from any third-parties, just not from unofficial resellers. Especially if the deal sounds to good to be true and costs less than on the official shop.   

Here is one reddit post where the co-founder recommends physically checking the hardware of Ledger wallets purchased from unofficial vendors:
Source: https://www.reddit.com/r/ledgerwallet/comments/auje8k/buy_a_ledger_nano_from_a_third_part_in_amazon_in/