A document published by the Treasury of the New Zealand government provides insights into the real life differences between firms who develop relationships with members of their supply chain, in contrast to those who pursue more arms length exchanges. Here is an extract, followed by a video produced by Toyota which provides more detail.

Toyota, as many other Japanese firms, maintains a small stable set of ’highly trusted’ dedicated suppliers, restricts competition for the various orders only to them, caring for their profitability and rewarding the best performing suppliers with a higher share of orders, while replacing those that fail to deliver the extremely high levels of contractible and non-contractible quality required.
— http://www.treasury.govt.nz/publications/research-policy/wp/2012/12-01/28.htm