Unite is included for free with the Pro bundle. However, additional fees may apply in your region for consultation, support, or testing accounts.
If you want to know what is Unite Developer Hub is, please check: What is the Unite Developer Hub
If you want to know what Unite is, please check: What is ON!Track Unite
If you are interested to know where can you find technical details about ON!Track Unite, please check: Where can I find technical details about ON!Track Unite?