JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0/js/bootstrap.min.js"></script>
 <div id="orgPrice" data-price="00,50"></div>
 
 <select id="subcode_060" class="custom-select custom-select-sm" data-description="UPGRADES" data-subdescription="X to Y" data-price="15.5055">
   <option value="0" selected>0</option>
   <option value="1">1</option>
   <option value="2">2</option>
   <option value="3">3</option>
   <option value="4">4</option>
   <option value="5">5</option>
</select>

<div id="total">0.00</div>

JavaScript

$("select").on("change", function () {

  var sum1 = parseFloat($(this).val()) * parseFloat($(this).data("price"));
  var sum2 = parseFloat($("#orgPrice").data("price"));
  var sum3 = parseFloat(sum1) + parseFloat(sum2);

  $("#total").text(sum3.toFixed(2));

});