And PowerBI is either free[1] or $10/month per user[2].
Having architected and implemented BI infrastructures using all three, their pricing models all tend to converge to the same ballpark once you get to a standard, fully loaded and integrated installation. But they all have different levers for their pricing sheets, so unique usage models can sometimes take advantage of that to get a substantially better deal. Licensing models that are amenable to minimal/opportunistic usage exist for Tableau and PowerBI, but Looker very deliberately prices out that usage model.
