On the site I looked at there were 14,000 listing for houses in Detroit, out of those 3,100 were below 20k, that's about 20% and of those 1000 of them were below 5k. That's a lot more than a few, other states are a lot different but most of the news stories about $1 houses relate to Detroit.
did you looked at foreclosures or prices in general
there are quite a few cheapies I agree dont forget to ajust Aussie $ to US $
and then compare as we are buying in $AUS
http://www.trulia.com/MI/Detroit/