I agree with Krill, the way you have it sounds less like conquering and more like 'become friends with this place so they're willing to sell you the authority".
For a true 'Conquer' feeling, I'd suggest something closer to this: The influence 'meter' could just be changed to progress, the job could be made so that it's high risk, high reward. And you don't have to pay when you finish conquering, instead you get a random slave to either keep, or sell.
The risk/reward feature of the job could be something like: High chance to reduce slave's health by a lot, based on their endurance stat, the chance of this happening could be reduced by high combat stats (Strength, Agility, and Magic). However, while there's a high risk to your slave, you get a 'good' slave when you finish. The quality, and maybe amount, increasing as you conquer more areas. And finally, you get a 'tribute' (ie: a small amount of income) for each area conquered.
My reasoning for these ideas is this: When conquering some place, you're usually fighting, thus there's a good chance the slave will end up in combat, and thus hurt. However, when you've conquered an area, you capture the one(s) in charge and choose what to do with them, keep, kill, sell. This way, instead of a way to waste your gold, it becomes a legitimate way to collect gold/slaves. You could even add basic loot random events (you get a random item now and then) when you have a slave working the job.
Just my thoughts on the idea.