DTube relies on the Steem blockchain for authentication, and according to that blockchain's FAQ: "To create an account on the blockchain, it costs STEEM tokens. When you create an account through Steemit.com, Steemit Inc. is supplying the tokens to pay the account creation fee. [...] The only way to have an account created via Steemit.com is to supply your email and phone number." If the previous holder of your email address or phone number was a Steem user, or if your phone is in an unsupported country or on an unsupported carrier, you will end up having to pay to create an account: "There is a third-party tool called SteemCreate that accepts credit cards, or BTC to create a Steem account. You do not need to have an existing Steem blockchain account to use the service, but there is a charge on top of the blockchain account creation fee for using the service." In turn, from that service's description: "Account creation cost is $45"