I sent Leica in Solms, Germany two of my lenses last summer. I tried to avoid it, and thought that the cost was too much. But the result was surprising. I needed new flanges and got ones with six-bit coding. They also took apart the lenses and cleaned the elements, removing spots from inside. They recalibrated each lens and even added a new red dot on the side where one was missing. They were, as you said, like new lenses. I'm pleased that I sent the lenses to them.
When an item is expensive as a new item, then even after getting used, the repair cost will stay very high. I sold my old Mercedes roadster because I was unable to maintain it. It needed very costly repair, even though I bought it as used for a very low price. Same with a Leica item.