But who chooses what the comparables are? Who picks the competitive neighborhood? Houses aren't bought based upon an algorithm. Houses are typically purchased on emotions (like the panic we see now). Understanding a market requires understanding the nuances that go with it. That's why appraisers are supposed to be geographically competent. At some point, judgment calls need to be made (an appraisal is, after all, an opinion). Who makes those? Who verifies the condition, and that it doesn't smell like cat pee? Who verifies the upgrading, the design quality, the landscaping and land value? Even if you develop a "simple computer program" to do that, someone has to recognize all the other parts of a house that don't show up in there. Where are you going to get that kind of data & consideration? That's right, from a person.