Sold Pluto at the Beginning of 800

In order to celebrate their son's success in getting his doctorate, Sean's parents took him on a trip to Antarctica. As a result, Sean accidentally fell into a crevasse and slid all the way into the bottomless dark abyss. When he woke up, he picked up an alien mobile phone. After turning it on, he was able to connect to the alien e-commerce website. Looking at the dazzling array of alien black technology products, he had no points in his account. So, he sold Pluto for 800 yuan...