It is because of the testing methodologies, not all the labs use the same methods, and each has their own set of ranges based on the test that is used to do the measuring. The last lab I worked at the normal range was 300-1100;critical low was 150 or below and critical high was 1900 or higher.

When they say that "cancers run in the 800 range" is irresponsible because it based on a lab that relative to those ranges for labs that use a specific methodology which your lab may not use. It cannot be applied to all methods.