Use form_alter to add placeholder text to a Views Exposed Filter min/max field
Found the solution!!! (here: https://www.drupal.org/node/2280069#comment-8844805)

  if (isset($form['field_listprice_value']['min'])) {
    $form['field_listprice_value']['min']['#attributes'] = array('placeholder' =&gt; array(t('Min Price')));
  }
  if (isset($form['field_listprice_value']['max'])) {
    $form['field_listprice_value']['max']['#attributes'] = array('placeholder' =&gt; array(t('Max Price')));
  }