Interesting thread with theories all around while missing the primary reason for lower aircraft prices.
Yes, ridiculous levels of regulation have raised operating costs and priced a few people out of the market while also making jobs scarcer domestically, but that is not the primary cause. The bottom line in the U.S. is that the pool of airplanes has not changed much while the
pool of potential buyers is only 53% of what it was in 1980. Sorry, was unable to find the original AvWeb link but I've seen the figures elsewhere too. Too, a very large percentage of that population may already be too old to consider buying another plane, and it's trending more in the same direction. Add in that Light Sport is sucking away potential buyers who don't want to hassle with medical issues, and the market picture for traditional GA aircraft is remarkably different than in decades past.
When you have the same number of planes (supply) chasing half the number of potential buyers (demand), something has gotta give and that "give" is price. Expect to see more and more older planes relegated to the parts bin over the coming decades as some become essentially worthless.
The good news is that for old farts like me still young enough to fly there are deals to be had.