Going back 6+ years on fauna classifieds, it seems that market prices drop by about half every 18-24 months.

Whether that has held true since the first pastel was available, or will hold true in the future.. *shrugs*, but the cumulative power of halving a price every two years is pretty big.

Supply and demand, people. Breed lots of spiders, sell 'em to lots of people who will them breed them and produce more will only force the market price lower and lower, unless new demand is created.. Essentially unless you can recruit a new herpetoculturist to the hobby for every hatchling you produce, prices for any particular morph will diminish and eventually level out somewhere around the cost to produce.