All You Need To Know About TLS Certificate For Onion Website
One of the first providers was DigiCert, offering certificate for onion domain, and the price was about 350$. It was not expensive for Facebook, so they implemented it in their onion website.
Thanks to Harrica, a Root CA Operator founded by Academic Network (GUnet) now it’s much cheaper to have TLS certificate for your onion website and operate more securely in deep wild web.

We already know that communication through TOR is already encrypted, so the question is why should we use TLS for onion website?
Our Community portal page about onion services give you a list of reasons why a service admin would need a TLS certificate as part of their implementation. Here are some of them:
Even we are talking about paid version, we really hope that in future providers like Lets Encrypt will be able to provide onion SSL certificate for FREE.
Also make sure you are doing it for onion v3 because Tor will no longer support v2 and support will be removed from the code base.