Improving margin is usually sought through negotiation with the supplier. The more effective route is understanding the industry's ecosystem and finding the point that is still uncontested.
A traditional market publishes no data; an online market publishes too much. Neither tells you what happens if you enter. The only reliable instrument is a small, real test.
A supplier who stays inside an organisation for years drifts into monopoly, and their prices drift away from the market. The answer is not to cut them off, it is to build competition without raising supply risk.
Suppliers are chosen on reputation, and the contract is usually one page. The result is that the established, reputable supplier carries more risk than the newcomer.
In a traditional organisation, a strategy is not carried out until it has its own budget line. The method that works, very small goals, small budgets, and evidence that makes the next step possible.