Market price for a BK2000 is $2200 - $2500. That would be what the seller is looking for. The price is dropping for this title in line with other games. This particular game is a "no brainer" for $2500.
A high end BK2000 might fetch $3200 tops. You might find a fastidious collector that wants a home use game for $3500 + but it is not a $4000 machine in any condition - unless it is a NIB.