I find that each dealer is different, and each deal is different. The dealers buy most of their used inventory at auction, so the prices are variable. Your bottom price is going to depend on what they actually paid for it.
That said, we saw 2000-2002 Foresters from $10K to $28K. All over the map! I wanted a 2001 or later (updated bumpers, paint, some minor interior changes) "S" or "Limited" trim. I found few Limited models available, so we set our sights on an S model. We found quite a few 2001 models with mileages ranging from 70K to 120K. Ironically, the one with 120K was in the worst condition (stained upholstery, chipped paint, filthy interior) was the priciest at $23K. Most asking prices were in the $17-19K range. I didn't want to pay much more than $15K. The first one we tried for was a 2001 S asking $18K, but the dealer would not come down much at all. We got stuck at $17K and there was no moving, so we let it go. They had another one with about 3000km's more mileage, but otherwise in just as good condition, also asking $18K. We ended up coming down to under $16K. Why the price difference? Probably (I don't know for sure, of course) they had less into the one we ended up buying.
So, you'll have to ignore the "black book" except to get an idea of range, and work on an individual basis. However, I personally would not go much over $15-16,000 for a 2001 Forester. It might take some time, but they're out there. We had to hammer on three of them before getting the one we wanted at the price we wanted.