Anecdotal evidence is not bad. Obviously someone sinking a billion or more into this has done their maths. There is no let up of building coming up all over Nairobi. Look at Bryan, Kadudu and some of NASA crew here..as early as 2006..they were shouting the bubble will burst..those are the days when a nice 3 bedroom in nicest places of Nairobi would go for 3-5m...now the same is 20-30m. The bubble has not burst. You're talking about a city with huge backlog of office/real estate. The bubble will burst 100 yrs from now.
Nairobi is clearly out there doing bigger things than any city in Africa - is it overdoing it - maybe - maybe not. All we need is for Uhuru to steer the country back to the path of stability and we should be fine.