The limit of foreign currency you can carry with you to Iran

Hello,

I travelled to Iran few times in the past couple of years and I got with me small amounts of Iranian products to sell in my country like saffron, caviar and honey.

I am willing to get more stuff on my next visit, and I am wondering what's the maximum amount of cash money I can bring in with me at the airport.

I mean is 25000 $ allowed or not? If not, whats the best way recommended to bring money for my purchases?

Thank you.