I've had very heated arguments in another (type specific) forum about valuations with people who refuse to accept the fact that their beloved aircraft is actully worth less than they paid for it.
Problem is that many people bought aircrafts or shares back in the days when old spam cans actually appreciated. It was a fluke, a strange anomaly that occurred for some years mainly due to demand, the good times that prevailed and the lack of newly manufactured aircraft. None of those factors exist today and that bubble market is gone.
But not only that. It used to be the case that if you bought an aircraft for 10K with a run out engine and then spent 20K on overhauling it, you could turn around and sell the whole mess for 30K. Engine funds were even something you could take out loans against. That's also gone or at least going.
And some of the most overpriced stuff I see are the shares. It's not uncommon to see a quarter share going for as much as an equivalent aircraft would cost on its own! Open any flying magazine and you'll see overpriced aircraft and shares re-listed and re-listed ad nauseum without the sellers taking the hint.
It has never been more of a buyers market and what you put in to an aircraft in overhaul or upgrades, you simply will not get back. This has been true for cars for decades, so it's actually about time aircraft aligned.
Buy outright now if you can afford, is all I can say. Never been a better time.