Yeah, I'm incredibly curious as well! I think it's a very cool project, but ball-parking development costs, my guess is the domain probably cost more than the product itself, assuming they didn't go down NIH-type rabbit holes.

Edit: And to be clear, I'm not even necessarily knocking that decision. Maybe an expensive TLD could make life easier for a project like this, since it could promote trust / buy-in, increasing usage at an early stage. ¯\_(ツ)_/¯