IMO, part of this pricing is hype. Boutique parts can be very pricey, especially if machining costs do not benefit from the economy of scale. Unless the manufacturer is copying a time proven circuit and modifying it, there could be significant time spent engineering the circuit, plus there are all kinds of esoteric build "tricks" that experienced designers/builders know and frequently don't share. Things like: wire routing,component layout, capacitive coupling, and stuff that's just plain weird like eddy currents and transformer core-saturation.
It may be a case of the 80/20 rule. You might be able to get 80% of the way there for 20% of the price, but the final 20% is REALLY gonna eat up some time and money.