barista, I don't know if you are using a script to generate these, but the first three on your list are incorrect. Your "last sale" price in these cases is the sale price of the land before it was subdivided and the houses built on the resulting plots. Check out the date of the last sale vs the date of construction.
I didn't check them all out, but I'd be suspicious of anything that appears to have fallen $0.5M (unless we're talking a multi-million dollar property).