After I traded with the merchant "Belethor General Trade Goods" in Whiterun several times, it seems that his cash has reached to zero. I went next 2 game days and was still at zero amount of cash, which, I had to do trading with other merchants in town, or simply travel to another city to do so. I wonder if the game's trading system is same as Fallouts', or are merchants able to re-generate his/her cash in few days?