You are correct on the amount of the costs but wrong about the ignorance of the council: it was fully aware of them but decided to go ahead anyway. I was part of a group that included many prominent architects who (many are retired) had no financial  interest in the issue. Councilor Alan Zelenka was the most vocal cheerleader for the rapid demolition; he appears to have a conflict of interest, at least implied: he has close ties to the local purveyors of high-energy efficient technology (read very expensive and somewhat untried). He also misrepresented the condition of the "old" City Hall, repeatedly.