I managed to learn just enough awk to parse search results from AutoTrader.com.
So, in the spirit of a near-parity Loonie, I have determined the following information
For used BMW 335is (plural, not the new coupe) between 2007 and 2010 within 500 miles of Buffalo NY, with at least 2k miles on the clock:
Generally:
Each Year Newer is worth $3250
Each 10k miles is worth $1400
Navigation is worth $825
CPO is worth $2000
Unfortunately the data wasn't good enough for me to figure out which cars had the Sport pkg and which did not. One would have to look at the pic of the steering wheels.
Deviations by Year:
2010s are usually $1400 above the modeled price
2009s are usually $500 below the modeled price
2008s are usually $1450 below the modeled price (looks like the best value is here)
2007s are usually $300 above the modeled price
Examples:
2009 CPO 335, 12298 miles, no navigation, asking 35.9k, model price is 38.6k
2007 non CPO 335, 25777 miles, asking $28.5k, model price $28.2k
Commentary and Scatter Plot
There is a LOT of variation in model value near the "round numbers" like $25k, $30k, etc. So one guy has a nice model asking $30k while another guy has a crappy example still asking $30k because its a round number. There is value to digging into the details.
Looks like 2008 examples with Navigation (hey, only $825...) are pretty reasonable deals right now. The average asking price is $30,185. Average mileage is 31k (miles...). 31% of them are CPO, and 40% of them have Navigation.
See attachment
Technical Detail:
The constant (ie: year zero, zero mile, non CPO, non nav car) is worth negative $6,497,018 for anyone who is curious.
R-squared is 83% / Correlation 91%
All factors are statistically significant with 99.75% confidence or higher.
