I read the survey on the HSBC and the results are definitely in US Dollars, not Qatar Riyals.

To put it into perspective, that means an annual salary of 730,000QAR (60,000QAR per month).

Possibly the survey included housing allowance, but I find that hard to believe since the survey is a measure of personal cash income. Housing allowance provides no financial cash benefit to the respondent, so that seems unlikely to me.

The survey results do not say where how the respondents were found, or how many were interviewed in Qatar.

Perhaps the respondents were all HSBC customers?
And the survey does say that as few as 30 people may have been interviewed per country in order to get accurate results ("A sample size of 30 or more respondents from each country was required for inclusion in the league tables, in order to be considered robust and indicative of the views and trends of the specific population it relates to".)