I really don’t understand who should buy the DEQX pre? What kind of a DIY speaker system would you even need to justify the cost? Even something with multi Purify woofers would dwarf the crossover in price. That just doesn’t make sense… and then you’ll still needs the amps. For about the same money you can get a pair of Genelec 8362As, throw in a streamer and your done for everything. That would be a way better deal.
First there are the people who have too much money. Price simply isn't an issue for them, appearance and ease of use will be. They will buy from a prestigious retail establishment.
Then there are those who aren't driven to build a DIY system at minimum cost or even at a performance/cost target. They may still look for some semblance of value, but are not all that price-sensitive. I know several people who reached an age where they bought a Jaguar because they thought it may be last last car they ever owned. Bear in mind that the US$12k figure is a retail sticker and will be part of a thoughtful pricing strategy. It's very hard to launch a product at $6k and then increase it to $12k, but much easier to launch at $12k and offer introductory discounts to see how sales progress. At $6k, the DEQX is not far from the Trinnov Nova once you've paid for all the extra channels of room EQ.
Then there are people like me. I'm a hobby woodworker who enjoys building speakers. Unfortunately, I'm completely incompetent at designing crossovers or anything else electrical, so DSP is the answer if I'm to build my own design. While a Flex Eight may well meet my needs, the DEQX surpasses them in style, and I would pay more for a product that I thought would last me to the end of my days. Sooner or later, I'll build another pair of speakers, because that's what I enjoy doing, and I'll be able to use the DEQX again.
Then there are the people who already have one or more pairs of passive speakers that they are very fond of and would like to try using with active DSP. Again, they may prefer something more up-scale than miniDSP.
Oh, and those Genelec's are pretty fugly!
I'm not saying that the categories I've suggested above are beyond criticism - just that it's different strokes for different folks.