your math is confusing.
on a high side the control board will save $40,000 in interest expense per year. Assuming a 30 year repayment period, and excluding the fact that the interest payments will diminish with time the city will pay $1,200,000 in interest. Equal to 2 years of our illustrious control boards time.
Even giving the control board 10 years more in power (which will NOT) happen. The city will only see a $400,000 savings. while that same control now unneeded
board will cost $ 6,000,000.