.ES, .IN, and .AU are all on our feature request list.
Does it cost Dynadot anything to have something available?
Yes, it does cost us money to add a new TLD to our system. First of all, some central registries (this especially applies to country code TLDs) have restrictions on who can become a registrar for their TLD.
Furthermore, each central registry runs things a little differently. These differences must be addressed before the TLD is fully integrated into our system. If it was only a matter of adding a checkbox, it would be a lot easier.