There are always "unpopular" suburbs on the fringes of cities that creeping suburbanization catches up with, a developer does an estate and 100 new homes are sold. VIOLA! Median price has a big boost. The same happens in inner suburbs where the old stuff gets knocked down and new ones are built.
None of this means that the crappy old house in the crappy street is worth any more though. I don't know the suburb you wrote about but I bet something like this has happened.
