The WSJ had a page like this for a while -- but pulled it. (http://www.realestatejournal.com/)
In the US, it is all public info -- purchase prices are filed with the county, along with Mortgage liens, etc. -- but it is inconveniently located in the county records building.
The net made it easy to check any neighborhood or specific home. But the WSJ price check tool shifted to this site:
Not nearly as helpgful . . .
Infact, King County in Washington State has all the information exposed thru their parcel viewer. Its quite useful and you can get the info relating to even the condo-owners with in a parcel/building.
It's at http://www.metrokc.gov/gis/mapportal/PViewer_main.htm
Can't speak to other states in US.