i know bro the cultural part is so important, nowadays you see people that are 40 years old and still are single and they are saying that i am proud that didn't gave birth to another human in this country with unknown future.Although I agree with you, but I think the economic aspect of the problem is not that big a factor. In fact, international data demonstrate that poorer countries have higher fertility rates. Look at Africa for example.
I think the main reason that Iran's fertility rate dropped so sharply is cultural. People started to value personal progress more than familial values and put individualism above societal norms. Meanwhile, a sharp increase in women's literacy rate and access to higher education are also responsible for this. After all, fertility rate depends on women. That aside, years of slogans like "fewer children better life", distributing free condoms, free vasectomies and tubectomies in 1990s played a huge role in dropping Iran's fertility rate. I remember when I was a child, there was a health center near our home and you could see the "fewer children better life" ads even on the exterior walls of the building and a sizable majority of people in Tehran believed (and continue to believe) that anything more than two children means bad prospects of good education, good job and other stuff in future for the child.
this is obviously a bad cultural feature recently formed in people believes and needs counter measures but as usual slogans are more important than actions in IR.
my point was that some people might have plans to marry and get children but unemployment is preventing them.