In my experience, a european couple can live comfortably in a nice 2bed flat and eating out a couple of times a week for 16,000. 

 

To lower the cost of living, don't live in a compound...there are lots of nice flats around...don't eat out at western restaurants etc...they suck your money away....go easy on the amount of alcohol you drink (expensive at hotels!)....don't pay for satellite tv. etc etc.

 

You can find a 2bed flat for say 7000 QR.  Car hire 1700QR (though better to buy if here for a while).  General living expenses 3500QR a month.  Still leaves you 3800QR for whatever else!