Month                Price               Source
May ’09             $170,000       Chicago Dispatcher
April ’09            $164,500        Chicago Dispatcher
March ’09           $165,000        Chicago Dispatcher
February ’09      $158,000        Chicago Dispatcher
Feb ’07               $  77,000        Chicago Tribune
2004                   >$40,000       Chicago Tribune
1991                     $28,000         Chicago Sun Times

(Chicago Dispatcher data are for the period ending on the 23rd of the indicated month).

I find it remarkable that this kind of real estate has continued to gain value, over 7% in 3 months, while most other kinds in Chicago seem to have declined.  There was, however, considerable fluctuation recently, with sales in late April running around $145,000, increasing to $175,000 on May 19 and 20. According to ads in the Dispatcher, you can lease your medallion out for $600 to $700 per month, a yield of close to 5% (in addition to any price appreciation which might occur).  There is, of course, some risk that the price might depreciate instead.