It's a little on the high-end, but Guhl put a lot of work into this and the ZX-14, and you have to remember that even successful motorcycle runs are limited to a few 10 thousands per year - with sport-tourers and sportbikes, they change so frequently that a huge amount of time and money can be spent to make something for them that is obsolete in just a few years and only applied to 20 or 30 thousand vehicles.
I think Don started this project with hacking the ZX14 CPU - once he had that, the Concours was either basically 'free' or more easy to figure out. Nonetheless he put a lot of time and knowhow into it.
You aren't paying for his time - you are paying for the years of experience he has that enabled him to reach this point.
Would I like it cheaper? Sure! Wouldn't we all but Don's gotta eat, buy cool toys, and he has to keep developing for other motorcycles as well.
The one thing that does make it seem expensive is you don't get the tools to do the tuning yourself - most of the time a $400 buys you the actual flashing device. I would LOVE to have the software/device to enable flashing and tuning on my own, but maybe those items are so specialized as to be cost-prohibitive for most of us.