Yeah it’s tax free and the wages are good but the expenses are also huge. You can’t own property in the main there and so every rents.
The rent costs are through the roof, living on The Pearl in a 2 bed apartment used to cost us north of £4k per month and our green fees at Doha GC was $1,000 per month for the Championship Course (ie full membership with a couples discount).
So despite the high pay and zero tax, the disposable income left for most people isn’t that much higher than it would be in a European capital. A head of Iceburg lettuce will set you back £5, beer £11-12, Hellmans mayo £5 etc etc, but petrol is cheap.