The eBay sellers seem to be more reputable than what is on Amazon. I recently bought a Sandisk extreme card supposedly from Sandisk themselves. The card I got came in a plastic bag in the case. No retail packaging, witness marks (wear) on the contacts, and a thumb/fingerprint on the label of the card. No warranty card or anything. Sold as new, was it used/refurbished or counterfeit?
So I order a slightly lesser spec SanDisk card from a seller on eBay that I bought before for about the same price and *bang* - retail card packaged, none of the signs of counterfeiting (poor printing, different fonts, lack of high pressure sealing marks on the card etc.). Card checks out with speed and capacity with various test programs.
Related food for thought:
https://petapixel.com/2018/10/02/lessons-from-losing-a-week-of-photos-to-memory-card-failure/