A story from a Norwegian customer
One world renowned customer needs large sized gate valves to be delivered with vertical type indicator post. In China only one factory could provide it, but its price level is quite high. We consulted with many other factories and found one of them could provide the valve, another one could deliver the indicator post part. With this combination offer the price level could be reduced by more than 30%. 
When the order finished, we arrange the indicator post part delivered to the valve factory and installed it, then supervise the testing. the valve functioned well together, and passed the 3rd party inspection assigned by the end user. 
Customer was satisfied and the business between us kept on growing.