This is a discussion. Keep that in mind.

First off, I would like to talk about transport immigrants and black death, mainly because, how Akrotiri suddenly "died".

Transport immigrants makes a port grow by the current value of population which is 1 % of it.

And Black death is 1% but it kills the population.

But because both kills the current value of population.
Lets say port y have 10,000,000 population.
And a cast of black death which would kill 100,000 which would leave 9,900,000 population.
Now we use transport immigrants on that port with that 9.9 mill population and instant of going back up to 10 mill, in only go up to 9.999 mill.

If we use Transport immigrants first and only later use black death it would be 10.01 mill and it would give the same result of 9.999 mill.

Of course this can be easily fixed by using about 100k to fix the missing 1000 population. This means that it would actually cost more to grow a port.
But since most port has more then 100 mill population this means after a cast of Transport it would take 1 mill more gold(or maybe more) to get to a point which it would look as if 1 black death was never cast.

But, at a lower value of population, black death will not be as effective as using gold to build up a port to return the missing population.
But now after the build up which would take a lot of money. The port has your own influence and such.

Lets not forget TI's are more expensive

Bad math?