Thought I'd toss some ideas out, that I've been thinking about for a while. These are mainly meant to be money sinks, but some of them would have a benefit for the player.
I'm trying to approach the problem by looking at money as a means to an end, rather than just something you use to make more money. Basically, the money you earn is used to fund another other aspects of the game.
First off, I was thinking that a merchant with some sort of random item selection. What I mean by that is basically like the whole item "gambling" system that was used in Diablo and other games. The player could choose to buy an expensive sword, but the player won't know what the sword actually is until after it is purchased. It could be something awesome, or it could be a regular Long Sword. Of course, this would be applied to other items (a random potion, a random misc item, etc.).
Second, adding a cost per person for exploration. Now, I've only been playing the alpha, so I don't know how things are setup in the current build. However, I believe that Xela was working on an exploration system (I could be wrong though). Anyway, the cost to explore an area would scale, based on the difficulty of the area. The reasoning behind this is that the characters must have the necessary supplies to make the trip and back. These supplies wouldn't show up in anyone's inventory, so there wouldn't be any need to create new items. An idea for the description would be something like "Tents, bedrolls, food, first aid kits (to save a character who is reduced to 0 HP), and other necessities for travel." Not a word for word description, but you get the general idea.
Third, incorporating item durability into most of the items. Sure, item durability is kind of a cheap way to force a money sink onto the player, but it does make sense. That 3000 gold dress might not last too long in the lines of work that are available for your girls. Thus, it will eventually become damaged and will need to be replaced. However, to help with micromanaging issues, the player would need an "auto-buy" function or a way to repair items in bulk.
Well, that's about it for now. I'll keep trying to come up with more ideas for the game.