Why might there be such a drastic difference in the per capita GDP of these selected countries of Southwest Asia (the Middle East) ?

There is a drastic difference in the per capita GDP of countries in Southwest Asia usually due to the presence of oil and also the size of the population. Countries like Saudi Arabia, Qatar, and the United Arab Emirates have high per capita GDP's due to their high oil and natural gas wealth as well as a relatively small population relative to the wealth level. Whereas countries like Yemen, Lebanon, or Syria have lower per capita GDP's due to their lack of significant fossil fuels or other major economic development.