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.
This is good for small suppliers who are often cash poor. When exchanges interact with other exchanges, you will see enormous changes. It takes different exchanges and ties them together. A buyer in, say, the North American auto exchange can communicate with a supplier plugged into the Deutsche Telekom exchange, with the P.O. in dollars and the supplier dealing in euros. The system will do all of the translations and transactions.