This makes sense and seems to fit. However:
This could be a problem and part of why someone on Noble would complain they are not getting their buildings built fast enough while on Immortal, buildings are, in comparison to tech achievement rates, much cheaper (since they haven't been adjusted.) By playing on Immortal for our tests, Joe and I have seen comparatively cheaper feeling buildings by a long ways compared to the tech achievement rates, which are stretched out. These need to be given the same arc as the units! (which incidentally matches the same arc as difficulty has for tech acheivement rates.)
Only the AI. And the bug is at prince, not monarch. Should be 95% if we're going off the other charts and patterns of progression as a guide. I'm not convinced this doubling of benefit for the AI is necessary to be honest. Maybe all these should be just a flat 100 to keep the AI set at what noble is set at without being adjusted further by game difficulty of the player. I think Joe would agree with me on that. But if we want the harder settings to be even harder, I can see why this is setup this way.