Dot io is a TLD (top level domain) and every domain marketplace like Namecheap, Godaddy etc have higher prices for dot io domains than dot com. This can either be due to higher demand or the higher fees are the reason. Often the higher demand is given as the reason for these prices, but there are reasons that suggest that the fees charged by the "Internet Computer Bureau" are the main driver of the cost. Nowhere as of not a dot io is less than US$30. I just checked Namecheap for an unregistered dot io domain and the price was US$33.