Just sold my 2001 M5 for around about $14k. It had 105k miles but was otherwise impeccable. $22-25k for a great one with half the miles seems like it would be a fair price to me.
Not sure why these cars get a bad rap for maintenance. I am pretty anal with maintenance, sure, but I haven't heard of major costly issues with examples that have been well-maintained. I'm sure there are outliers, but the problems that I've heard all come from people paying $20k for a 10-year-old M5 and expecting maintenance on par with a $20k new car. YMMV.
(Of course I had an 850i as well that never had any expensive problems, so who knows. That car can be a bit of a money pit.)
Why a 2002-3 versus the '01? There was a mid-model refresh after 2000, but that included the 2001s as well. I think the only difference from 2001 on was an upgrade at some point to DVD-based nav instead of the old CD nav.