What expression indicates a much-needed solution to a problem?

The expression "Just what the doctor ordered" is often used to indicate that something is precisely what is required to solve a particular problem or meet a specific need. This phrase implies that the solution is both appropriate and beneficial, similar to how a doctor prescribes medicine tailored to a patient's needs. It conveys satisfaction and relief that what has been provided is ideal in addressing an issue at hand.

On the other hand, the other phrases do not carry the same meaning of a beneficial solution. "Will cost you an arm and a leg" suggests that something is very expensive, indicating a drawback rather than a needed solution. "Exactly what was needed" is a valid statement but lacks the idiomatic expression that conveys a sense of appropriateness tied to a remedy. Meanwhile, "A far cry from" means something is significantly different from what is expected or required, which is contrary to finding a solution.