Value isn't just money. It's what you're willing to give up, whether that's time, priorities, or something else. When two goals clash, finding common ground means each side decides what they'll sacrifice to make the deal work.
The reason why a stated cost works is because the value you put on something is quite literally what you're willing to give up for it. Now, it's not always a literal cost, meaning it's not always about money. Sometimes there are other kinds of costs associated with this kind of finding of common ground. For instance, sometimes the cost is reprioritizing some of your priorities. It's about agreeing on what comes first when two priorities collide. And what each person, each party is willing to give up in order to honor that agreement.
