First of all, it is a fact that Chinese aunts robbed gold, which led to a booming business in gold shops. The gold shop will replenish the goods immediately after it is sold, and the profit difference in the middle is considerable.
Selling and replenishing all the time will naturally reduce the inventory cost.
The price of gold can't keep rising, can it? If it goes up after a while, it will naturally make all the money, although this process may not be immediate.