Pro bono doesn't always necessarily mean "for free" or "no fee" - could be reduced fees.
Besides this, there's probably filling fees to the court; I also suspect there's outside work required (think research for current or prior cases - PACER comes to mind), which is not necessarily covered by regular "lawyer fees"
Besides this, there's probably filling fees to the court; I also suspect there's outside work required (think research for current or prior cases - PACER comes to mind), which is not necessarily covered by regular "lawyer fees"