A modern military costs money, especially if one is developing a capable air force and navy. This are big ticket items. Let of us for a moment look at what is being spent by states bordering the Persian/Arabian Gulf, as this seems to be the flashpoint “de jure.”
Saudi Arabia is the big spender there with 67.6 billion spend on defense in 2018 (source: SIPRI 2019 fact sheet). This actually makes it the third largest defense budget in the world, ahead of India, France, Russia, UK, Germany, etc. It spends 8.8% of its GDP on defense.
Some other Gulf states are also spending heavily. Oman spends 12.1% of its GDP on defense, although its GDP is small. Bahrain spends 4.1% of its GDP on defense. In comparison the U.S. spends 3.2% of its GDP on defense, China 1.9%, Russia 4.3%, Iraq 3.9%, Ukraine 3.4%, France 2.3%, UK 1.8% and Germany 1.2%.
In contrast, Iran spends 13.2 billion (or 19.6 billion in 2019 according to IISS). This is 3.1% to 4.6% of Iran’s GDP. This is around 20% to 30% of what Saudi Arabia spends and around 2% to 3% of what the U.S. spends.
The per capita spending is higher for China and Russia, beyond 7-8% actually, this can be calculated. You will not get accurate figures for authoritarian regimes anyway, making these comparisons somewhat meaningless (for non democratic societies, based on the CPI index, 2018 figures).