function my_em_add_fee($paypal_vars, $EM_Booking, $EM_Gateway_Paypal){
 $amount = 30;
 if ( !empty($amount) ){
  $itemcount = (count($EM_Booking->get_tickets_bookings()->tickets_bookings) + 1);
  $paypal_vars['item_name_'.$itemcount] = wp_kses_data("Paypal Fee");
  $paypal_vars['quantity_'.$itemcount] = 1;
  $paypal_vars['amount_'.$itemcount] = $amount;
 }
 return $paypal_vars;
}
add_filter('em_gateway_paypal_get_paypal_vars','my_em_add_fee',1,3);