Client vs Consultancy

Throughout the process of organising the event I'm working on, I've had a fair bit to do with the client both directly and indirectly and I've been blown away by the dynamics of he client/consultancy relationship. It does seem at times that there is an us and them mentality and to a large extent it seems the hostility is fueled by the client. In many instances we are collaborating with staff from the client and in my opinion it seems that the processes being undertaken create huge inefficiencies. The client often changes requirements, disputes budgets and provides inconsistent guidance on things like branding and wording in publications. Approval is required frequently on even the smallest decisions which may cause up to a weeks delay on making things happen. At times when we work together it feels like we're competing rather than supporting each other. Now that it's getting so close to the event it's getting really frustrating and it's really made me feel that if I ever manage my own consultancy I would be sure to clarify where responsibility lies for different areas, specify details early to avoid long approval procedures and be clear on deadlines for the sake of the reputation and budget of both the client and consultancy.