I agree in principle, but the estimates for my own home on Redfin would beg to differ. The value of my condo at the time I purchased it seems to fluctuate every month. When I bought it I was below Redfin’s estimate by a few thousand, now it says I overpaid by like 30 thousand.
Just to be clear, I was referring to the estimate of the property at a certain fixed point in time (my purchase date) changing over time. I do expect current market price to change for my home. I was just saying that these sites will estimate a value that differs and shifts, even estimates of periods during which actual market price is an available data point. March 2017 may look like a great investment when you checked in January 2018, but really bad when you check in October 2018.
Anyway, I agree with you that the market is just what people are willing to pay.