.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.
And I have also requested .au domains for Australia. (.com.au, .info.au, .org.au)
In fact, while we are here, why not add the whole lot and be done with it.
Does it cost Dynadot anything to have something available?
If it does cost and no one wants it then I understand why Dynadot wants to know if there is some demand for it first.
Otherwise if the only cost is to add an extra checkbox and checkbox item on a particular page, then why not add it. Get everything possible and that way everyone will be very happy.