They sustain this level of wealth for one reason only, the black gold that lies beneath the surface - ore. This ore is a vital ingredient to the Imperiums infrastructure - Plasteel. It is used to make anything from a school to an Adeptus Astartes armour.
This planet isn't just a place for the rich to play about, it is also a prison planet - convicts, murderers any crime known to man has been commited by the damned workers that are shipped in to work the mines and live in the filthy Hives. Mining shifts can last weeks and can either be miles underground in sweltering heat or working the open mines that blemish the surface, where the weather is harsh and as unforgiving as the Imperial Guardsmen that police the planet on tour of duty.
Uprisings are few and far between, but they do happen, but such is the level of intell and Guardsmen they are felled quickly and without mercy. Public executions are regular to purge the hives of this kind of Heresy.
The Commisars have become lazy and do not have the Imperiam at the for-front of there mind or defenses, although they are not tainted they are more interested in keeping there blessed rich lifestyle in order. Corruption is rife among the wealthy beurocrats, traders and high society.
Local militia keeps control of escaping workers/hivescum looking for better life. They supply troops for IG duty all over the galaxy but because of the small population they get absorbed into regiments as opposed to making there own. Sometimes they are made into special ops squads as they have a vast array of skills that have been trained into them at the strictest and highest levels. The training is rigorous as the planet has a mixed climate with extreme conditions. Khaleraaq Vets are among some of the most revered men in the IG and often end up in Commissar roles, as they are highly intelligent, hardy and don't shirk any responsibility.
This is a planet that has never seen war of an great significance, never been over run with xenos and never seen the dark plight of Chaos mark it’s unfaltered past. The planet is so vital to the Imperium it has its own sanctioned psykers to weed out any Heresy that might lurk in the dirty dark corners. This is its greatest defense and also its greatest weakness...