Debounce MacBook pro Keybboard
Without knowing if Apple Techs fully evaluated the state of your system (you seem to have asked someone the repair cost), in the past batteries will swell and cause odd keyboard behavior before proceeding to various other bad effects including:


  Warping the back cover
  Leaking acid into the internals


Not saying I am right or wrong, but you have a chance to get ahead of this if it is true.