Well, we both know that you haven't used it for 20 years. It's sitting in a corner covered with rust. I used that machine for parts, but I was damaged by loss of the three other machines and all that inventory. You're still talking. When you use the magic word to develop facts, the other side may not agree, but they probably won't see you as greedy, either.
Negotiations can take real effort to prepare and carry out.
However, the effort is worth spending. Occasionally, clients see that as a betrayal, but those clients are wrong. So hold off on tantrums. When disputes come along, and they always do, think negotiation. Follow the rules, and use the magic word.