The final subtlety is that not every right has a monetary price that can function as an equivalent. A legally recognized substitute must be shown to replace the relevant right; the mere fact that a benefit was enjoyed is insufficient.
Classical examples concern marital benefits, invalid judicial testimony leading to separation, and certain consequences of wrongful killing. These illustrate that compensability of the underlying right must be established independently. Mahr or ʿuqr may be due for a different legal reason and must not be equated with a universal price for every benefit.
Summary: Adāʾ concerns the original duty and qaḍāʾ its substitute. Each can be complete or deficient. Valid compensation and remedies depend on a recognized legal cause, not superficial resemblance.