Is this even possible and why should IRAN buying Bitcoin in the country higher than what we have online? Because of the volatility, we may have some arbitrary opportunity or wide in the gap of bitcoin's pricing across the exchange but that doesn't mean it should be up to 100% different. Bitcoin is decentralized and if such opportunity exists the arbitrage traders will take the advantage and make huge money from IRAN by buying from USA exchange and sell at IRAN exchange.
While I don't know where OP got the information that bitcoin in Iran is worth 50%-100% more(not saying it's fake news), trading bitcoin is banned[1] in Iran. Meaning, it's going to be very very difficult for you if you're interested in holding some bitcoin hence why there's probably a huge price premium.
Yes, Bitcoin is decentralized, but you're still going to need to buy it from somewhere; and that's mostly going to include fiat on ramps.
[1]
https://www.tasnimnews.com/en/news/2019/07/08/2049108/trading-bitcoin-illegal-in-iran-official-warns