With ball pythons, as far as i've seen, 90% of the time the female is more expensive. With bananas i've heard that it's because males are much more rare. NERD had a video about coral glows, stating that first gen coral glows only rarely throw a male. You could have 3-4 clutches from a first gen banana or coral glow and only get one or two males. Don't quote me on that 3-4 number I just know that males are rare with the first gen bananas and coral glows and you can have a few clutches with only one or two males.