Leaving McKinsey's specific brand value aside, people always miss the value of "hiring (business) consultants". You basically get insider knowledge about how competitors businesses and systems work. So if you ask for advice about how to build a healthcare app for smartphones, you hire McKinsey (or whomever) to tell you "about the market". But really, they are just telling you about what they saw at other competitors. For some business decisions, it is very valuable.
