what Florida counties have the cheapest per acre cost

Prices for Florida agricultural land skyrocketed last year as
developers and speculators hunted for precious real estate.

From May 2004 to May 2005, agricultural land prices rose an average 50
percent to 88 percent in Florida

The 2005 Florida Land Value Survey results indicated that the value of
all types of agricultural land increased substantially in all regions
of the state from 2004 to 2005.

http://www.agbuscenter.ifas.ufl.edu/landuse/pdffiles/luse05.pdf - here
you can find the survey results which provides estimates for land
value per acre, by geographic region and land use, 2004 and 2005