Just wanted to share with everyone a recent exchange I had with a fellow M3post member...this was about one week ago.
trex858: Really cool study you compiled! I am looking at buying a used 2009 and was wondering if you can run the numbers for me? 2009, Space gray, DCT, 37k miles.
overdose: Thanks for your PM and comment! I'd be glad to run the numbers but I'm obligated to let you know that the sample set for MY2009 is very small - only 35. Again, take it with a grain of salt and use it as a benchmark.
That being said, the equation for your specific request is...
Y = -0.2706x + 56024 with a standard error of 4409.
That means your M3 with 37k miles would estimate to around $46,012. A really good deal would be at $41,603 and a very expensive one would be $50,421 or higher.
trex858: Awesome, thank you. The dealer wants $46,998 and $42,000 is exactly what i want to pay for it so from what i can see your numbers are on target based on the current market.