Right now, it's the recession that's dropped a bomb on everything. You used to be able to vaguely predict how much a morph would drop each year based on the type of mutation (recessives hold their value particularly well, while co-doms can drop quite dramatically, depending on their popularity).
It all boils down to supply and demand. Right now, demand is down--not because people don't WANT them, but because they simply can't afford them. Once the economy picks up again well, then demand will go back up, as people will be able to buy those mutations they've been coveting while their wallets were empty. I doubt we will see prices actually rise--the ball market isn't used to having that ever happen, so it's hard to imagine someone having the courage to raise prices other than in very extreme cases (which are unlikely to occur), but at the very least we should see a slow-down in depreciation back to pre-recession times.
After all, the ball python reproduction rate isn't changing, and more people continue to become interested in keeping and breeding herps as a hobby.
So, in conclusion, it's all about the following factors:
General economy
What the originator chose to price a brand new morph at
How publicized a brand new morph is
How extreme a brand new morph is (spider versus chocolate)
Potential in combinations for a morph (better combos = more demand)
How easy the morph is to reproduce (dominant, co-dom, recessive)
How big the breeder's name is/how nice the individual animals are
So, you can see a male pastel for $75, or $200 --if it's 200, it's probably an eye-popping special animal from NERD or something. The low priced animal is NOT necessarily inferior--it could just have been produced by a new breeder who's starting out and building a name, or by someone who is merely a hobbyist and just wants to move the offspring out fast so they don't have to spend time on their care. It does pay to look around.
It is wise to be cautious, because sometimes a low price tag can point to inferior stock, or inferior care (some unethical sellers do not retain enough cash to care for their collections properly, so try to sell quickly both for money and to get the excess stock out before it get too sick to sell).