Emerson, Strider, Hinderer - heck, even Chris Reeve all have prices that are well out of proportion with their build quality and/or materials. It's nothing new. They've been outgunned by other companies well before the influx of Chinese manufacturers putting out unique designs and collaborations.
What they have, though, is reputation, style, and, most importantly, niche markets (within the already niche market that is quality folding knives). You can get a mechanically superior knife for less, and you can get a knife with better materials for less, but you can't get their knives for less. Their knives are iconic and have avid fans - you won't find many (if any) people that will tell you that a XM-24 is a more practical choice than a Reate, but arguing for practicality goes out the window once you break the $250 mark on folding knives and hit that point of notably diminishing returns. Once you step out of a certain price range, you're paying for the style, reputation, and/or perception of the knife.
Materials and build quality can be had for cheap. I have a S35VN-bladed knife with a titanium framelock (+ steel insert) that runs on ceramic bearings with a ceramic detent ball. I paid $60 for it on the exchange. It's smoother than any Emerson, Strider, Hinderer, or Chris Reeve that I've ever owned. It's perfectly centered, has flawless lockup, and flips like a dream. That said, I still pine for a double-thumb-lug Large Insingo with snakewood inlays because the feel and design of the knife speaks to me in such a way that I would toss the aforementioned flipper in the garbage without a second thought if I had the disposable income to justify buying that Sebenza. If my tastes were different, that same sentiment would apply to some certain Hinderer/Strider/Emerson/etc.
TLDR: They persist because people want them. Nobody is arguing that their knives are an objectively superior value - they would instead argue that value is subjective.