Interestingly, theres been quite a lot of negative facebook commentary about the price the current owner is asking.
I think people forget it takes killing / using a damaged M3 to make one of these, So automatically it's at least 25k worth going by regular M3 coupe prices.
A decent E46 late model touring is generally close to 10k worth, rougher ones are cheaper of course.
Then you have the time to sort the M3 body panels and paint them, that looked to be very well done and would have cost a fair bit of coin if you were to try replicate it.
Electrics, coding, and fine tuning of everything transferred over to the touring chassis isn't a 5 minute job, especially to get everything working like it's a factory car.
Other stuff like the physical work changing parts, subframe work, exhaust work, all the suspension installed, certification too.
You need to have experience with BMWs to do such a build properly, not many people in the country could pull it off.
It's up to the owner to find the price they want anyway, given the above I think he'd get close to the asking price with the right buyer that sees it for what it is.