Hello all, I think the optimal way is getting to near 100 first, then getting chunks of 100 after that.
Using https://politicsandwar.com/tools/infra(unless that tool is somewhat unprecise), we can do the following:
The value of infrastructure purchased, starting from the amount 1850 and ending at the amount 1900 is: $1,177,424.50
The value of infrastructure purchased, starting from the amount 1900 and ending at the amount 2000 is: $2,479,630.00
Total with first 50 infra buying: $3,657,054.50
The value of infrastructure purchased, starting from the amount 1850 and ending at the amount 1950 is: $2,354,849.00
The value of infrastructure purchased, starting from the amount 1950 and ending at the amount 2000 is: $1,303,793.50
Total with first 100 infra buying: $3,658,642.50
Buying to near 100 is better with my example. Not sure if 1050 to 1200 is gonna happen that too, or others examples, just made one.