I think it is a pity that producing raw material is less and less rewarding when you grow in the game. In comparision, having a strong army is very rewarding because gold and stuff value are bigger when you explore new dungeons whereas producing is only a stable income.
I suggest to implement new Oracle "spells" to allow building more buildings (+1 mine, +1 farm, ...) as it already exist for wood, stone and water production. These new spells could require stuff that flood the market and have no more value today (dices, fire elements, ...), which would help regulate their price.