Buyers either single-source everything and discover the risk during a crisis, or dual-source everything and dilute their volume until neither supplier prioritises them. Both are avoidable.
Where a second supplier earns its cost
- The part is critical and has a long replacement lead time.
- The supplier has become dependent on you, or you on them, to an uncomfortable degree.
- Your volume is large enough that splitting it still leaves each supplier motivated.
- You have had one quality incident that was expensive rather than annoying.
Where it costs more than it protects
On low-value parts with many available sources, where you could switch in weeks anyway. And on anything requiring dedicated tooling, where a second supplier means a second mould, a second qualification cycle and two golden samples to keep aligned over time.
A cheaper middle path: qualify a second supplier without ordering from them. You carry the qualification cost once and keep the option, without splitting volume or duplicating tooling.