Well there’s overhead like cost of administering the claims etc etc so actually if it were literally replacing the house every 20 years the annual premium would be like house$ / 10 not 20.

But if it gets even remotely close to that point the yearly insurance is a significant portions of the house worth and it’s obviously not affordable/insurable - whatever term one wants to use.

At that point if one can’t self insure then they can’t afford the house