It's a nice car, I probably understand a bit. Here is my opinion about it (just opinion, yours will vary).
- if you are still enjoying the car even just used once a week/month. AND you don't need the money. AND not expecting it to appreciate. Just keep on enjoying it.
- if you are not enjoying it. AND need the money OR can use the money for something you would enjoy more. Sell it to the price you want it.
- cars are generally bad investments, but some get lucky
My background on the my opinion above. We bought a R34 GTT Skyline long time ago (almost 2 decades ago), I really liked it a lot. I tried to sell it several times (3 times), my wife knew that I enjoyed it a lot so she discouraged me to sell it on those times. Fast forward about 2022, we are not using the car too much... have definitely enjoyed the car through the years and my wife is not doing well health wise. We decided to sell it, luckily the value has appreciated 2x our purchase price. Actually a dealer bought it sight unseen, just photos and seemed they have sold in quickly for a better price (that is ok, we wanted a hassle free transaction as we didn't have time on our hands to do private sale). So for our M5 we are less attached to it, I tried to sell it (1 time already). My wife said to just keep it and enjoy it, so I guess we will follow the same route as the Skyline. Enjoy it while I can, then when we can't or need the money we will sell it.