<div class="col-lg-4">
  <label>Pacote do Evento</label>
  <select class="form-control" id="pacotes_id" name="pacotes_id">
    <?php foreach ($pacote as $t):?>
      <option value="<?php echo $t->idPacote; ?>" data-valor-pacote="<?php echo $t->valorPacote; ?>"><?php echo $t->descricao; ?></option>
    <?php endforeach;?>
  </select>
  <input type="text" name="totalEvento" id="totalEvento" class="form-control" value="" readonly>
</div>

<script type="text/javascript">
$(document).ready(function(){
	$("#pacotes_id").on('change', function () {
		$('#totalEvento').val($(this).attr('data-valor-pacote'));
	});
});