The Relationship Between Suppliers and Buyers

A lot of tomes people will say, well, what's the real value that you're getting here from them? A companyis could be doing it all themselves and steat of out sources to someone else in a way that's ally integrated into their business. How do you judge the power of a the suppliers and buyers? I guess a lot of scuttle, but it's a big part of that. Also, sometimes figuring out what just going up th the stream.