I'm under the impression: Because it's all in the marketing. There is no incentive to build a "proper high-end" fully active system for 500 Euro when you're outcompeted on price and marketing by a manufacturer offering a "pretty good but not quite high-end" 400 Euro system that sounds good enough for all but a few (and then you're all of a sudden competing with much more expensive systems as well).
Also, your estimate seems off to me. I don't know your personal background, but prototyping a good-sounding speaker cabinet takes time beyond a few hours. Even more if you're aiming for mass production. Add to that the DSP + n-channel Amp board, this will be expensive, even when building 10000, AND it is not trivial circuitry to design.
Also, "proper high-end" is a relative term. When researching which speakers to build and where to source chassis, I found a nearby "proper high-end" manufacturer integrating realtime measurements of cone movement into their DSP corrections...