There are just too many out there by now. Go to any given expo and half the tables will be ball pythons. They are the most numerous species on Morph Market by a wide margin. Craigslist/classifieds/rescues are overflowing with them. Doesn't even matter if they're morphs (you can get a lot of single genes and even multi-gene combos for $100 or less if you know where to look), the market is simply that over-saturated.
To give a personal example, I got my banana BP a little over 2 years ago for $250, which seemed about the standard price at the time. Now? You can get a banana with one or even two other genes in the mix for half that price.