The market is hardly in a place to make money on anything now. It is a buyer's market for almost everything in the luxury hobby areas. Many are selling, money is tight, Christmas is coming, the free government cash has run out, the bill for it is due, and the economic headwinds are not favorable. Tactile is fairly well known. I wasn't aware of the Archer, but it looks like a nice knife. Your friend could probably flip as many of these as he could sell by buying them at $599 and selling them at $400 or so. I'm sure what he loses on a per-unit basis he could make up on volume of sales.
As the old line goes - if you want to make a small fortune making or selling knives, it's real easy. First, you start with a large fortune, then you start making or selling knives.