An interesting thing to note here is that this price situation does not seem to be the same for all PC components. Drives, for instance, don't get more expensive as they get old. PC RAM seems to have an "economic dynamic" all it's own where it starts out outrageously expensive, then as newer faster types emerge it gets cheaper for a while, and eventually as it gets "old" it starts getting scarce since companies stop making it, and the price starts going back up. Obviously the reason for this is that PC's seem to age very quickly, more quickly than most consumers and companies would like, so they tend to hang on to their "old" machines, making the RAM still useful. But where RAM is a component that is tied directly to the machines it's made for, things like Drives and video cards are not, and can be easily upgraded, so they don't have the same life cycle as the RAM. It's also this tie to the MOBO that makes most people eventually upgrade to a newer PC; to "get more speed" they have to get a newer computer eventually.
It's all a very interesting and unique part of the IT industry.