Honestly, the whole following represents to me one of the biggest scams in the business. Much like a number of other companies, they have a cult following that believes in the hype that Peter Q has spread, hype which is not based on solid engineering but marketing trash. I've heard one of their overpriced highest-level kits (put together exactly according to plan, in a couple setups, full AN upstream, etc.) and it sounded exactly as I expected. Poor drivers and unbraced cabinet contribute to a poorly resolving speaker with lousy dispersion, resonant/high distortion bass, and clearly not at all "realistic" or true to the recording. Despite what others may say, I found it nowhere "musical", unless you like the sound of broken instruments and muffled singers.
You'll find that many of the cultish owners tend to describe them as "musical" and "PRAT-ty", however. I find that to be more of an excuse because they fail so miserably at all the things good speakers should do. The price is based on massive markup for a collection of overpriced crossover parts which are sourced elsewhere... somehow, AN has convinced people that silver wire and oil caps are more important than solid design.
You're right, the kit is easily doable, because it is so simple. It's not difficult to put together a poorly braced box. Reasonable cost? That's up for you to decide.. I would recommend hearing/seeing for yourself though. Other kits offered, including ones on this forum such as the Ellis 1801 offer FAR better parts and, imo, ultimately better sound and value. If you want to splurge on a pricey but top-notch kit, go for the Linkwitz Orion. Unless you're dead-set and sucked into the AN marketing, I would really encourage you to look at some of these other options.