throwaway for obvious reasons. I've worked with Deloitte, PwC, KPMG, and other big consultancies for a diverse range of reasons (regulation audits, security reviews, staff augmentations, etc.) and the value you get for the money you're paying is pretty insane. I'd say the value you're getting is probably 20% of the price you're paying, and I'm being optimistic. You can get good value if you know the people you're hiring, if you scope your project well, and if you have clear expectations. But let me tell you, nobody knows how to do this, unless they've been on the other side.
Now, you don't always have a choice, the expertise is sometimes there, or you need one of the big four to do a prior audit before a real audit from another big four. But be prepared to have a team of OK people who will spend a lot of time producing slides and organize unproductive meetings with lots of other people (including yours) to give out a false sense of "we're making progress here". You'll have to do the PM'ing and be extremely strict with what you want from them, and you'll have to be ready to collaborate heavily. What I mean by this is: don't wait for them to ask questions, you'll have to do most of the work of onboarding them, almost like they're your coworker except that they don't have connections with the folks they need to work with, they don't have access to internal stuff, they don't know how to get there.
Now, you don't always have a choice, the expertise is sometimes there, or you need one of the big four to do a prior audit before a real audit from another big four. But be prepared to have a team of OK people who will spend a lot of time producing slides and organize unproductive meetings with lots of other people (including yours) to give out a false sense of "we're making progress here". You'll have to do the PM'ing and be extremely strict with what you want from them, and you'll have to be ready to collaborate heavily. What I mean by this is: don't wait for them to ask questions, you'll have to do most of the work of onboarding them, almost like they're your coworker except that they don't have connections with the folks they need to work with, they don't have access to internal stuff, they don't know how to get there.