Keep in mind that EquityHackr is only one fish in the sea when it comes to who can buy your car.
If you’re serious about selling then get quotes from all your local BMW dealers as well as any of the major groups than can buy BMW’s. And while you can’t sell to Carvana/CarMax/Vroom etc. you can still get quotes as a reference point.
While it’s unlikely you’ll have a lot of equity I wouldn’t stop trying yet just because one buyer came back low.