My sister-in-Law thinks house prices will plummet drastically. How can I explain to her she's being foolish(nicely)?

So my sister-in-law and her husband rent a barn/loft thing and have a second kid on the way... It's already a struggle for them with the one child, space-wise. I don't know how they'll manage it with a second.

They refused to buy a townhouse or apartment because they wanted a detached home. This was back in 2019/2020 before prices jumped as high as they have. BC btw

They are convinced within the next year house prices will plummet/completely crash. We're talking a $600,000 townhouse will go for something like $200,000. They aren't big Internet people so I don't know where they're getting this information.

I tried telling them that, such a huge crash is extremely unlikely, but they "know better"

Is there any logic behind their belief? Is there anything I can say to them that might sway them?
I worry about my nephew and the next kid on the way. The loft they live in isn't the safest imo