I don't know exactly what you mean about a dark male bp, but a good captive born bp usually runs you around 50-100 dollars. Usually depending on age, pattern, color(high gold, high white, etc), stuff like that. If you go to shows, however, you can pick up some good deals there. Such as good bp's that are like 20 dollars.

Temperment...nothing too different or notable between the two. Only difference between male and females is usually the size. Females get bigger usually. That's about it though. Most bp's, male or female, are shy docile snakes.