Exactly, the it's the Land, not the structure. If the land is practically worthless, there's a ton of money left over to build on it.
The most telling in the prices you posted is that 758 sq. ft. house for 527k:
> Last sold: Jan 1973 for $25,000
That's $135,939.19 inflation adjusted to 2016 dollars. Where'd the remaining $390k of value come from (assuming house is in same relative shape.)