I’m in the same boat. It doesn’t seem to have much value.
Some sites don’t accept it as a trade, or they offer you <$300 for it. The same sites are giving $250 for the SS models.
I looked at swappa, and it’s not much better.
I’m debating skipping out on series 4 because I’ll be selling my ceramic Apple Watch Edition at such a loss, and the grey ceramic is a gorgeous watch.