It also completely ignores the personal aspect of value. If I lived next door to my sister that is value for me since she can watch the kids if I need to run ou

It also completely ignores the personal aspect of value. If I lived next door to my sister that is value for me since she can watch the kids if I need to run out for something but she won't do that for anyone else. Likewise sentimental value, a 4th generation home can influence people's price a lot.