How much should an 8-series cost?

I have loved the 8's since I was a kid in the 90's. I think I may have to seriously consider picking one up. I don't need perfection, or low mileage. I need something that can get me to work and back on most days, that is generally awesome. How much are the cheaper 840's going for? No 850 for me, prefer the m62 over the m60, but would not be opposed to an ls1 swap as a long term backup plan...