Clearly, the most expensive upgrade to an airframe is the retrofit of a new autopilot. While many new autopilots will precisely fly the airplane from wheels up to the landing flare, their costs could exceed the value of the airframe. Still, we cant think of many upgrades that more enhance safety, airframe value and utility.
Modern autopilots compliment the capabilities of nav management systems such as Garmins gold standard 430/530 series. They’ll fly GPS flight plans in the horizontal and vertical, climbing, descending and leveling the airplane and some even fly oval tracks in holding, all while providing voice prompts to keep the pilot in the loop. No surprise that such automation isn’t cheap.