I played in a D&D campaign, Eberron, where the DM just said, "Money isn't a factor. Just assume whatever normal goods, services, or equipment you're purchasing for yourself is within your means. It went just fine. We didn't bother keeping track of coins or other treasures beyond some magic items or useful equipment we found. We were all agents of the state and doing our jobs was motivation enough. Now 5th edition D&D is fairly infamous for gold being meaningless passed level four or five, but it was nice not being concerned with it at all.
The long and short of it is the players need to make characters motivated to engage with the campaign as you presented it to them. For Dark Heresy, or any game set in the Warhammer 40k universe, every human being has their place in society to achieve the Emperor's grand plan. Maybe they're a farmer on an agri world, maybe they're toiling in the depths of a hive planet making knives for the Astra Militarum, or maybe they spend all day polishing all that gold armor for the Custodes. It's a quasi-feudal/fascist society, and the players are in a unique position of being outside the social norms but in a sanctioned way. They can't afford to make the Inquisitor mad because then what becomes of them? Where will they go? How will they survive? The players need to decide what motivates them to work for the Inquisitor. Maybe it will improve their social station? Perhaps they're fanatics who believe they're going to purge the Imperium of xenos and heretics. It's up to the player to decide.
