I bought the Fairphone 3 a few weeks before the 4 came out, but was able to sell it for nearly the original price. I wasn't happy with it anyway (and the FP4 didn't have a headphone jack so I got an S10e second hand, which also works 10x better — I'm happy to make compromises on top of paying extra but there are limits). Maybe that works for you too if it's still good as new