Well the problem might be "self solving" to some degree
LA / mag engines are no longer made, and the mag heads don't have "that" good a track record for cracking. As long as the aftermarket supports them, "fine." But we all know a bit about aftermarket quality, good and bad.
And this country used up a LOT of potential cores with the "cash for clunkers" program. Would be interesting to know just how many magnums got junked?
So as the LA / mag platform gets older, and less supported in parts, it too will become more expensive for parts, and less available on the used market. Around here, low miles mag engines are rare, and a 5.9 is a LOT more rare than a 5.2
Transmissions are their own problem, as A518s won't fit without tunnel work, and seems like most the pickups were 4x4. 2wd or vans are few between, as are A500's
Transmissions alone have sunk a deal or two for me on an engine, as you sometimes get a seller who wants to sell the whole vehicle, or won't split a (4x4) gearbox from a potential engine.
I recently spoke with a local yard in Spokane about magnums and price. They didn't have much of anything in magnums, but "would be glad" to fix me up with a hemi.......for a preposterous price. He indicated they had hemis "all over the place" meaning lots OF them, but he didn't seem to be willing to adjust the price!!!!
