The 600k figure is total population, including expatriates (in fact the figure seems to be rising rapidly, and you will find takers at 750-800k).
The Qatari population is very small, and probably no more than 150k - I can't recall exact voting figures in the referendum on the constitution, but seem to recall they were broadly in line with this assumption. Given that the only "owners" of Qatar's GDP are the Qataris themselves, then the true GDP per head of national population (ie excluding the expats) rises dramatically to USD100k plus.
Where do I apply for a passport?!?!?