A pair of articles here. One long one about the process of producing an R1 release, and a short one about the state of the market in 2005.
The second article gives 30,000-50,000 copies as a range for strong R1 titles, with Appleseed and Ghibli titles selling over 100,000.* In contrast, B-list titles seem to rarely break 20,000.
*I can confirm this second claim, as I recently got an opusdata trial account and pulled sales figures for a bunch of anime movies, which I will post sometime soon. Unfortunately, their extended weekly charts, which would be invaluable for US market research, cost something in the range of $1000 (or more if you want the backlog), which I’m not paying.