Dev, I share your sentiments and thoughts, and also own a Ref3. I actually prefer the horizontal board layout of the ref5, and in some ways cannot understand why they ever used vertical boards, however with the cover on the preamp, I usually do not dwell on it!
At this level of quality and performance, improvements are going to be slight as you mention. I think they are charging more because they can. I will borrow one to try in my setup sometime, but I am not in a hurry either.