To go the extra mile means to go beyond what is necessary or expected, which is what they are admitting makes sense in this sentence.
Consider the staetement "Lets admit that it makes sense, maybe even good business sense, to work harder than what is necessary or expected for him.". Based on this statement, is "Lets admit that it makes sense, maybe even good business sense, to go the extra mile for him." a true statement? Yes/no/unknown