It sounds like you have made some modifications to the Blu-Jet AT3015 side-dresser in FS25. The price range you mentioned, $16,700-$30,000, suggests a wide range of customizability in terms of extension options and additional features available for the side-dresser. The ability to adjust the rim color configuration and add a light/flasher bar option allows for further personalization to suit individual preferences.
With a capacity of 3880 liters, the Blu-Jet AT3015 side-dresser seems to offer a decent amount of fertilizing capability for its size. However, it's worth noting that the AI and assisted steering features may require manual adjustments before starting, as you mentioned that they start with the wrong auto width and headlands settings.
Overall, it appears that while the side-dresser may have a few configurations missing and may not be perfect, it still functions well and looks fine in the game. It's great to hear that you were able to find a converted version that you were able to revert back to the original Blu-Jet design. Experimenting with modifications and adjustments can often enhance the gameplay experience and provide a more customized feel to your farming operations.