First off, thanks for putting this together Hiku. Very thorough and objective analysis of the content the game provides.
I think my biggest takeaway though, is that each of the two individual entries are comparable to Awakening in terms of content, and so the graphic in the OP (though understandable a joke) isn't really apt. The issue is more that the value decreases with each consecutive game played. Playing either Birthright or Conquest will leave a similar impression to Awakening, while playing the other game will be around 50% retreading. That's a poor value if you refuse to buy digital, but a wash if you download it, from what I can tell.
Revelations seems to be the bigger issue, since the amount of content is far less than either of the two original games. Without playing it, I can't judge if the the additional story content is worth the added price, but objectively the 3rd version is a poor value based on stages and characters alone.
That being said...I definitely feel there are a lot of intangible factors that are a bit tougher to take into account, which makes me believe looking at characters and stages alone might not be painting the full picture. For example, if the characters and story are more interesting to me, the unique or new classes are well-designed, or if the new objectives add to the gameplay. Mostly subjective, I admit, but it makes the comparison a bit more complicated.
For me, even if I hadn't pre-ordered the special edition, I wouldn't have an issue paying $80, as I know this is a game I'll sink hundreds of hours into on subsequent playthroughs. I think for more casual fans of the franchise who would only want one playthrough, a new $40 game comparable to Awakening is nothing to really worry about. For hardcore fans that need the full experience, I think it depends how you quantify the differences in the games.