Every seller insists it's "Genuine HP" in factory sealed cartons and...it's not. The same thing happens with pens. Cheap knock-offs, every time. Reading the reviews on Amazon is unhelpful, because the reviews are polluted with apparently deliberate misinformation. It's got to the point where I either order Apple chargers from Apple directly or go to one of their retail stores in person, and I always buy inkjet cartridges in person. (I don't like fires and I don't like clogged inkjet nozzles.)
Amazon is great for lots of things, but not small, easily counterfeited, safety critical items.