This comes as a surprise to a lot of people who never been to UAE.
The percentage of uber-rich natives is grossly overestated by the popular image of the country. Nor there are that many really rich expats, unless with businesses outside of UAE, and who only come there to spend.
UAE is not a good place to make money in, but it's often a first choice for MNCs to setup in the region, as anywhere else in the region is even worse.
Only 10%-15% of the UAE population is somewhat close to American middle income standards.