Northern Lake County I can pretty much guarantee you won't find land for less than 25K/acre - same with McHenry. Farmland in Boone County is going for 15K+/acre, JoDaviess is seeing 6K+/acre right now and climbing. I'm not sure about DeKalb, but I'm gonna guess somewhere in the 8-10K/acre range.

Unless you've got a lot of cash, your best bet is still to head South of Chicago. Way south.