While it has been mentioned many times in the industry, and many times in this thread, supply and demand are a big driver for the prices of Ball Python mutations. With that said, lets take a closer look at the supply end of that statement to better answer the OP's original question. The comparison of Bearded Dragons to Ball Pythons is a poor for one main reason: Supply. A Bearded Dragon female can lay up to 35 eggs, versus a large clutch of 13 for a large Ball Python female. That is almost a 3:1 ratio, meaning that you can produce 3 times as many new Beardie morphs in the same amount of time. A large colony of Bearded Dragons can be kept in a much smaller space than can a colony of Ball Pythons that would produce the same quantity of babies. Lastly, Bearded Dragon females have a much higher possibility of laying year after year versus a Ball Python female that can potentially take every other season off. That being the case, it is possible that the ratio of offspring between the two species is closer to 6:1. This same event has also occured with other species of snakes, such as Retics, Burms and corn snakes. These species can lay very large clutches of eggs, and in some cases, more than once per season. Those factors allow for the "manufacturing" and distribution of new morphs a much quicker process, thereby allowing the SUPPLY to increase much quicker.

With all of the above stated, there are many other reasons, which could probably encompass an entire book on the mathmatica and economics of reptile breeding, that contribute to the rise and fall of prices on mutations of different species of reptiles. However, I hope that some of what I wrote about above will help to answer your question of why are Ball Python morphs so "expensive".