To get legit products from Amazon is like winning a scratch off. It's not rare, just not common.
i've been around the sun enough times to know that when things are too cheap, there's usually a reason. history is full of pills being sold that weren't what they claimed to be on the box.
We know most of the reason though, and that is that the insurance model of the US is completely broken and blows prices completely out of the water. The Amazon pharma prices are only 'too cheap' relative to the base US inflated price. They're much closer to the prices you see in perfectly peer level countries in Europe where they have perfectly safe drugs.
Once you have any mtbung that falls into that category, 90% of the benefits go away because if you have to go in for that one thing anyway, it’s mostly less hassle just to get everything there rather than split things up between multiple pharmacies.