Size 14 is low in stock in many items. Perhaps buy more 14 size to sell.
They buy less extremely large sizes because quite frankly there aren’t that many size 14s looking to buy clothing online. The company would be making too much of a loss if they overstock certain sizes and have to cut down the prices by exuberant amounts. I often see size 12 and above rarely selling well and the prices end up being slashed ridiculously low just to clear stock. Don’t forget the company needs to make money to sustain.