I found another (did not found it in other posts sorry if it is the case) : When i am guildmaster of the tradesman (or crafstman, don't remember) i can buy packages of raw materials (like silver,cotton,...) I buy one, go into one of my shops managed by the ai, and i let only the ai manage the production (and not the sale! otherwise when i put the package, the ai put it in a cart and go sell it at the market).
Here is the thrick : i put it into the store of the shop, select the button to unpack it, wait 1 or 2 sec, and the ai put it with the item to be sold in the shop, i select to unpack .... and hurray !! i gained 12items (ie silver) and the crate is still with the items to be sold. I just have to do it again and again ...and ...oh damn its not funny :p