I’m sure they’re just trying to put on a good front. Deep down they are probably sick over it.
What they don’t know, and what you shouldn’t bother explaining (why cause them more pain?) is that taking into account inflation and the value of the dollar, it will likely never reach that “value” again. Ever. It might see the number $600k again in 20 years (5 is laughable), but again that will be far from today’s dollars.
And if they really do like living there and can afford it, who cares?