“Reaped a massive windfall” if and only if they sell their house. The problem is unless they’re both looking to sell and move into a lower COL area, that doesn’t do them much good.

My house today is worth 2x what I paid for it a decade ago. Which is great except for the fact that housing costs around here are closer to 3-4x what they were a decade ago. Even if I wanted to sell, I couldn’t find any livable housing for the same price within the same area.