If you click on the number sold (under the number available) it will show when each item sold and for how much.
Seems seller started selling them at $19.95 and then jacked up the price by $10 every couple of days (selling coins all the while) until now those 50c coins are at $99.95 (2 have sold at this price). Of course they could just be shill buyers. Any real coin collector would just noodle one for themselves.