Find element only inside this parent element
$('.listing-summary').each(function(){
var summaryprice = $('.price.at-summary').text();
if ( summaryprice.length < 30 ) {
$(this).find('span.expiry_msg').addClass('x-m-expired').fadeIn(400);
}
else {
$(this).find('span.expiry_msg').fadeIn(400);
}
});