It doesn't say the equity is $450K. It says the net worth of the household -- which includes equity in your home, savings, 401k, pension value, etc.
Feel better now ?
A good rule of thumb for net worth is to dive the household's income by 10 and multiply by the average age of you and your spouse. If your net worth is above that, then you might be able to avoid a diet of dogfood in retirement.
I still find it hard to believe. I think the median balance in a 401k is less than $50,000. Some defined benefit pensions, however, are worth a lot -- but how can they be valued by the average household. People only know approximately what they will get a month in retirement. They don't know the net present value of their future benefit.