The referenced link will provide lot sales data dating back to 2007 for you look over. In Marysville, lots have been selling for $35-45k but they where 2,900 - for the zero lot line homes in the Meadows. In comparison, lots in 2009 sold for as high as $60K for a 6,000 sq/ft lot.
It really depends on what you're wanting to purchase: recreational, suitable for building, or farm. The first question I ask when working with someone who is looking at lots is: Are you wanting to build on the property?
If the answer is yes, mot of the time it is, then a whole list of other question follow regarding water source, sewer or septic, building permits, access to the property, how wet is the soil, and time frames.