I'm pretty new to the BMW realm. I could not believe how low the blue book was on these cars when I scoped out my 525i. Certainly with the build quality and performance hear car give they are worth much more to people like us.
What I speculate with the low blue book values is dealer service rates and how much attention these cars require. Because I am a mechanic, I reap the benefits from these low blue book values. It's the people that buy these cars not knowing what they are, people who take their vehicles to the dealer for everything, that become convinced they are a bottomless pit for cash and thus brings down the value. Only disadvantage to me and I'm sure many others here is feeling locked in due to kbb values.
Don't sell it for anything less than you want out of it. It took me over a year to sell my rsx for what I wanted, and it brought me to my e39. Patience will reward you and I hope tax season will help expedite things for you. Good luck with the sale