Iran is a top 20 economy in the world as measured by GDP Purchasing Power Parity (PPP) and should be included in G20 according to their own criteria.
According to International Monitary Fund, World Bank and CIA World Factbook, Iran ranks in the top 20 world economies.
Iran outranks Saudi Arabia, Argentina and South Africa and even Australia (in the World Bank rankings) who are members of the G20, but it is not included. Even if we consider the (now obsolete) nominal GDP rankings where local inflation and cost of living is not counted, Iran still scores higher than Argentina and South Africa.
We all know that despite the empty rhetoric of “free markets” and “Capitalism” no such thing actually exists. A bunch of mostly former colonial powers pretend to have “faith” in capitalism and free markets so long as they end up on top. If it looks like they may not be best served by free markets, they will promptly scrap its principles for themselves. If it looks like non-client states like Iran are making inroads in their little economic club in spite of sanctions, pressure and every NON-free market dirty trick in the book, they will simply keep them out artificially.
How long do they think these games can last?