#states not working properly in IE 9
I found the answer from this Link. So Internet Explorers never accepts element value as integer. I changed my code as follows it's working for me,

$price['#states'] = array(
  'visible' =&gt; array(
    ':input[id="edit-field-paid-event-und"]' =&gt; array('value' =&gt; '1'),
  ),
);