The original poster is simply wrong. First, most of the gift cards are selling close to or below face value. Second, people have other reasons besides "money laundering" for doing so. It can be eBay cashback promos, Paypal cashback promos, etc.
The original poster provided an eBay link, and my personal experience confirms that gift cards for US-only services relevant to non-US residents are sold for above face value on online marketplaces accessible to non-US residents. I only disagree about the reason, I don’t necessarily see anything nefarious about selling them at higher prices than face value.
