if (function_exists('wpcf7')) {
  function cf7_extra_fields_func()
  {
    if (is_singular('excursions')) {
      $price = get_post_meta(get_the_ID(), 'exc_price', true);
      $html = '';
      $html .= '<input class="wpcf7-form-control wpcf7-hidden" type="hidden" name="product-title" value="'.get_the_title().'" />';
      $html .= '<input class="wpcf7-form-control wpcf7-hidden" type="hidden" name="exc-price" value="' . esc_attr($price)  . '" />';
      return $html;
    }
  }
  wpcf7_add_form_tag('cf7_extra_fields', 'cf7_extra_fields_func');
}