It's nominal GDP per capita was above Taiwan, Turkiye, South Korea, and all of Eastern Europe.
If the stuff that happened to Iran in our timeline didn't happened in the 1980s-2000s, it probably could have seen an economic boom comparable to what SK and Taiwan saw in the 1990s - especially becuase the leadership in 1980s South Korea and Taiwan were equally as authoritarian as that in Iran back then.
Other similar losers from that era were the DRC, Syria (before the civil war it was roughly on par with Turkiye), the Ivory Coast (it was France's premier financial hub in Franafrique before the civil war), and Pakistan (it's GDP per capita was significantly above China's until the 1990s, and Pakistani advisors helped industrialize significant portions of the Gulf).
The economic sanctions are a symptom not the cause.