Elon says[1] the AI assistant will be part of X premium for $16/month.
More importantly:
>Grok is an AI modeled after the Hitchhiker’s Guide to the Galaxy, so intended to answer almost anything and, far harder, even suggest what questions to ask!
I'm a big fan of both, but using a Robert Heinlein word to name something you say is based on a Douglas Adams idea is weird.