Here's an idea: instead of "grinding", why not make your tedious chores involve (almost literally) "farming"? For example, make the player do something to start a process -- plant a seed, prune a fruit tree, sneak a dragon egg into the giant eagle's nest so she'll sit on it, etc -- and then require that a certain amount of time pass before the benefit is ready to be picked up. This could be a specified number of game turns, or even real-world elapsed time. Instead of grinding with repetitive actions, the player has to plan ahead and think about multitasking -- what can he do while waiting for the prize. You still accomplish your design goal, though, which I think I understand to be that you want the player to be able to guarantee a certain quantity of treasure is produced.
