Because, what you forget is that Drop is not about just American buyers. Drop has many customers in various parts of the world (like me in Canada), and since Drop has unbeatable shipping costs, it makes these purchases compelling and competitive for many buyers outside the USA. Amazon.com and eBay sellers as well as online knives retailers, often charge an arm and a leg for shipping to other places besides the USA.
A recent example is that I was looking for a $54.99 slipjoint on some of these very well known knife retailers, and shipping to Canada was $18 USD and up. So I can tell you with certitude, even if a knife was $15 or even $20 more on Drop compared to say, KnivesShipFree (they don't ship free to the rest of the world by the way, just the US), it would still be way better for me to buy it on Drop.
And seeing that usually Drop's price is the same or a few bucks more than other places, then the knives sold on Drop are an awesome deal for me, and I suspect for many other buyers around the world. So, you just gotta stop thinking about items sold here on Drop as being aimed at just American buyers; this is the online way, the goal for Drop is to sell everywhere.