Quick Answer Key: NO
There is no extra charge to set up your white label domain. Once your account is set up you will be able to set up and activate your own personal domain for your clients to review content. Here is a step-by-step guide for setting up your white label: https://help.mixbloom.com/quick-start-guide!/pMcS3sC2dmU1GVWbtKRXoL/setting-up-your-white-label-domain/kjUVfrtW3E65BUB4yNcVYd