Nope you don't it is like this:Thanks guys. Just to show off my mathematical ineptitude:
Say I have a city producing 30 hammers (shields dammit!) a turn, and it's building something that costs 12. After one turn, I cash rush it.
Turn one: 30/120 hammers produced
Turn two: 90 hammers bought
Turn three: Production finished, 30 hammers go to something else
Turn four: Production would have finished naturally, 30 hammers go to something else
Are you losing a turn's worth of hammers in there, the hammers that you would have produced the turn you pay?
Turn 1: 30/120
Start Turn 2: Buy building: 120/120
End Turn 2: Still building

Turn 3: Finish build and start new one with the 30 left from previous build - the carryover is limited to the cost of the build, i.e. 240/120 will lead to a carryover of 120 and 2400/120 will still lead to a carryover of 120. The lost

