So in your analogy, it's up to the farmer to set the price for the potatoes. In this case, was it Gamestop who was setting the price? Or rather, the shareholders themselves... that is, the people who were buying the stock in the first place?
This is how stocks worth: its only worth as much as what someone is willing to pay for it (shorting not included).
Whether his first asking price is £2.00 £12.00 the market will quickly decide the level. If potato's are the hype root vegetable, many buyers will appear, but if carrots are in fashion, the price of potato's must fall until in order to attract buyers