Price seams about right for sticker. When I traded in my '07 550i two years ago, it had 62,000 miles and all the options of the one you are looking at except comfort access and I had the SMG transmission, and I got $21,500 on the trade-in. Add two more years of depreciation, 45,000 more miles, and dealer profit, and $15,000 stickers feels about right. I would think that could go for around $12,500.
However, getting into a BMW with that type of mileage, expect a decent amount of repairs (e.g. sensors, suspension, cooling system, etc. . .) and budget for them annually.