I know i also get the precious reputation out of this quest, but the gold part hardly covers the cost of acquiring the slave in the first place.

Since this is probably the hardest quest type and requires a lot of minmaxing and attention by the player the rewards should probably be much more enticing.

The quest I'm refering to:

It may just be me missing how to complete this easily, so if someone has suggestions they would be appreciated.

It is possible for the slave market to have a slave that can be used for less than 200 gold at least for the easy version that has at most 1 class requirement and minimal stat requirements. For medium and hard ones you have to train them and than it's not worth doing.

I find that about 30% of the time you can just buy a slave and turn them in for a profit.  Even at higher quest difficulties you are still making money off them while you train them so I'd say it's worth it as long as training them is something you like doing in the first place.  Most of the time the quests are doable in a week and you can use captured bandits making the cost of the servant what you can sell them for rather than what you buy them for.  The ones that really aren't worth it are the 5 day services with stringent requirements.