Your gem costs for time are off.
You can't simply say that 6 gold mines take 65.4 combined days to build and then punch 65.4 days into the calculator.
Because unlike resources you can't over buy time. If something takes 1h to complete you have to pay the gem cost for 1h of time. You cannot for example buy 1 week of time and some how apply it to future updates.
This matters because the cost per gem increases with the less time you buy. For example 1h will cost you 20 gems. 1 week will cost you 1000 gems or a bit less than 6 gems per hour.
As a result rushing 6 gold mines will actually cost over 16k gems; double the amount than your calculation.



