displaying meta key value with wp_page_menu

There is no easy way to alter the vale of each li in the wp_page_menu but there is a way to do it without creating your own function or custom walker using the_title filter hook.

so create your function , something like this:

function custom_menu_title($title,$post_id){
  return $title . ' ' . get_post_meta($post_id,'meta_key',true);
}

and you hook it before you call wp_page_menu and remove it right after so:

add_filter('the_title','custom_menu_title',10,2);
wp_page_menu(array(...));
remove_filter('the_title','custom_menu_title',10,2);