I have ten thumbs and nearly turned my Forte Is into a pile of Klipsch spare parts in my first attempt at installing Crites crossovers. Thankfully I got it right the second time and was even able to swap out the tweeter and midrange diaphragms, but that tested the limits of my technical skill. Not to mention that I live in an apartment and don't have room for the power tools that I don't know how to use. Not everybody is capable of building functional speakers, never mind something that will compete with what $50k will buy you.
As far as the cost of high end audio goes: the prices are what the market will bear. If there are customers willing to spend $25k on a Mark Levinson amplifier, why drop the price to $2,500? Not to mention that parts are a small part of the expense: electroacoustic engineers don't come cheap, nor does the equipment required to produce several hundred or several thousand pairs of speakers.