The explanation of difference is the market. Qataris, like most people around the world, pay the minimum amount they can to have someone do a satisfactory job. Because of the world economy, that means they can get a guy over here to mop floors for very little, but someone who is a professor in a university demands a higher salary.

Other places have similar disparities based on jobs. Look at how much a professional footballer makes in the UK verses a janitor.