To calculate how much money you will need to get over the infra jump , divide the total money you would lose with the jump which in the case of the 1000 infra jump is 22.2% of your current infra bill by your Taxes Paid Per Day per citizen and divide by 10. That’s how much infra you need
so for example if 22.2% of my infra bill is 60000 and my taxes would be say 36.67 per person so
60000/36.67=1636
1636/10=163.6
so to get over the jump I would need to buy 163.6 infra.
when I did the 1k jump i had to buy about 60-70 infra. Assuming you have 5 factorys and construction (and if you don't have it, get it asap) it should only cost you
around 1-2 million. More money is nice though