The aviation and aerospace exchange with Boeing, Lockheed Martin, Raytheon, and BAe is one. The chemical and energy industry exchanges are also pretty demanding. Early on, they have been able to drive out some of the inconsistencies in their spend. GM, for example, found that one of its suppliers had 24 different contracts with GM at different sites with different dollar values for exactly the same stuff. GM was able to use the exchange to drive one price for the item.
Exchanges enforce the contract model, which allows different pricing models for different reasons.
If you're Chrysler, you only see Chrysler prices. So there's no overlap. Exchanges are also set up to do invoices and payments. Let's say you are a supplier, and you want to factor what you just received or sold. Systems can factor automatically.