<form>
    <select name="package" id="package">
        <option data-price="100000" data-discount="10">Paket 1</option>
        <option data-price="150000" data-discount="10">Paket 2</option>
        <option data-price="200000" data-discount="10">Paket 3</option>
    </select>

    <div>
        <label for="price">Harga</label>
        <input type="text" name="price" readonly />
        <br>
        <label for="price">Discount</label>
        <input type="text" name="discount" readonly />
        <br>
        <h4>Total: <span id="total">0</span></h4>
    </div>

</form>

$('#package').on('change', function(){
  // ambil data dari elemen option yang dipilih
  const price = $('#package option:selected').data('price');
  const discount = $('#package option:selected').data('discount');
  
  // kalkulasi total harga
  const totalDiscount = (price * discount/100)
  const total = price - totalDiscount;
  
  // tampilkan data ke element
  $('[name=price]').val(price);
  $('[name=discount]').val(totalDiscount);
  
  $('#total').text(`Rp ${total}`);
});