Why the hell is the game so expensive?

I sold my loose copy back in July for $90 (which was market value) and the price has literally doubled since. I was shocked to see this price. The graph shows a massive price spike (which happens to be right after I sold my copy lol) Any reason why it's all of a sudden so expensive?

I sold my loose copy back in July for $90 (which was market value) and the price has literally doubled since. I was shocked to see this price. The graph shows a massive price spike (which happens to be right after I sold my copy lol) Any reason why it's all of a sudden so expensive?