JSFiddle - React, Tailwind, and code Playground

HTML

<div id="calc">

	<label>Формат бумаги</label>
	<select class="form-control" id="paper">
		<option value="10">А2</option>
		<option value="20">А3</option>
	</select>
	
	<label>Тип бумаги</label>
	<select class="form-control" id="paper-type">
		<option value="1">Глянцевая</option>
		<option value="2">Матовая</option>
	</select>

	<label>Листов в упаковке</label>
	<input type="text" class="form-control" id="paper-amount" data-price="1">
		
	<div>
		<span id="totalprice">0</span> руб.
	</div>
		
</div>

JavaScript

jQuery(function ($) {
  $("#calc .form-control").on("input", function () {
    var paper = new Number($("#paper option:selected").val())
    var type = new Number($("#paper-type option:selected").val())

    var amount = new Number($("#paper-amount").val())
    var amount_price = new Number($("#paper-amount").attr("data-price"))

    var total = paper * (amount * amount_price) * type
    var str = total
    //	console.log( 'From string:',  );

    $("#totalprice").text(parseInt(str).toLocaleString("ru-RU"))
  })
})