Constraints in one dimension can allow unconstrained movement in another dimension. I use this all of the time in my revenue consulting. A classic example: given fixed costs, if you constrain margin, price must be unconstrained and be free to move up or down. If you constrain price, then margin must be free to fluctuate.

The error is when the client has goal like "We need to sell at $X to keep up with competitors and our margin needs to be Y" while costs are unable to change.

That is two competing mutually exclusive goals. I use the financial reality of these constraints to help get at the bottom of their true goals.