I think there are 3 general ways a Consulting organization can bring value:

1. Bring in actual expertise, which every large company has in droves. Operation, Finance, Strategy... you name it!

2. Help work on a thorny problem that the company's leadership doesn't really want to tackle themselves, or doesn't have the staff to put on it. Includes "right sizing"

3. Give credibility. If MBB said so, it must be true -> now your CEO can get his pet project approved by the board

I suspect many projects are a little bit of every one of these categories btw. And yes, they do provide real value. There wouldn't be such a large industry of 'overpriced' consultants otherwise.

So I am actually working in a large chemical company, and have heard presentations by consultants from PWC and EY before. The big value added for me was their industry knowledge, not necessarily the analysis or skills. Consultants and their firms have access to lots of private industry knowledge of competitors, and while they can't present that data, they are able to present to a company their benchmarked status (how they stack up). This to me was the most valuable aspect a consultant provieds to a large firm.

I'm nowin the process of applying to consulting firms because I have seen the value of the broad industry knowledge that is gained from working there.