The recession is taking a toll on finances at Tampa International Airport, especially on its single biggest revenue source: parking. Since Oct. 1, parking revenues are down 16 percent from a year earlier — steeper than the 10 percent drop in passengers. TIA executive director Louis Miller says more travelers are parking in the cheaper garages or skipping airport parking by asking friends or neighbors for a ride. Next year's budget will be finished in August and it's "not looking great, either,'' he told the airport's governing board Thursday.