JSFiddle - React, Tailwind, and code Playground

HTML

<div class="card-container">
        <div class="card">
            <img src="img/teplitsa.jpg" alt="">
            <div class="card-title">
                <h2>Теплица <b>«Стандарт»</b></h2>
            </div>
                <div class="inputs-form">
                    <h3>Выберите каркас:</h3>
                    <label>
                        <input type="radio" name="size" class="form-radio" data-price="13500" checked>   
                        <span><b>Размер:</b> 3x4</span>
                    </label>
                    <label>
                        <input type="radio" name="size" class="form-radio" data-price="17500">
                        <span><b>Размер:</b> 3x6</span>
                    </label>
                    <label>
                        <input type="radio" name="size" class="form-radio" data-price="21500">
                        <span><b>Размер:</b> 3x8</span>
                    </label>
                    <label>
                        <input type="radio" name="size" class="form-radio" data-price="22500">
                        <span><b>Размер:</b> 3x10</span>
                    </label>
                    <h3>Выберите поликарбонат:</h3>
                    <label>
                        <input type="radio" name="material" class="form-radio" data-price="3000" checked>    
                        <span>Эконом</span>
                    </label>
                    <label>
                        <input type="radio" name="material" class="form-radio" data-price="4000">    
                        <span>Простой</span>
                    </label>
                    <label>
                        <input type="radio" name="material" class="form-radio" data-price="5000">    
                        <span>Усиленный</span>
                    </label>
                    <label>
                        <input type="radio" name="material" class="form-radio" data-price="6000">    
                        <span>Супер...

CSS

body {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
}
.card-container {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
}
.card {
    width: 300px;
    text-align: center;
    box-shadow: 0 7px 20px rgba(0, 0, 0, 0.2);
}
.card img {
    margin-top: 20px;
    width: 260px;
}
.card-title {
    margin: 0 21px;
    margin-top: 15px;
}
.card-title h2 {
    text-align: left;
    font-size: 23px;
    font-weight: 700;
}
.inputs-form {
    margin: 0 23px;
    margin-top: 15px;
}
.inputs-form h3 {
    margin: 10px 0;
    text-align: left;
    font-size: 18px;
    font-weight: 400;
    color: #ff0063;
}
label {
    display: flex;
    align-items: center;
}
.form-radio {
    width: 20px;
    height: 20px;
    margin: 3px 0;
    margin-right: 15px;
    cursor: pointer;
}
label > span {
    font-size: 18px;
    font-weight: 400;
    cursor: pointer;
}
.inputs-form p {
    margin: 15px 0;
    text-align: left;
    font-size: 20px;
    font-weight: 700;
}
.totalPrice {
    font-size: 20px;
    font-weight: 700;
    color: #ff0063;
}
.modal-form {
    margin-bottom: 15px;
}
.modal-form {
  padding: 10px 40px;
  background: pink;
  border: none;
  cursor: pointer;
  outline: none;
}
.modal-form:hover {
  background: #ffa2b2;
}

JavaScript

var storage = 0,
    radioButtons = document.querySelectorAll('.form-radio'),
    totalPriceEl = document.querySelector('.totalPrice'),
    modalForm = document.getElementById('modal-form'),
    modalWindow = document.getElementById('modal-window');

radioButtons.forEach(function (item) {
  // Добавляем событие на клик
  item.addEventListener('click', function (e) {
    //При клике считываем все активные Radio
    var totalPrice = 0;
    radioButtons.forEach(function (item) {
      // Прибавляем к итоговой сумме значение Radio
      if (item.checked) {
        totalPrice += +item.getAttribute('data-price');
      }
    });
    // Вставляем его в DOM
    totalPriceEl.innerText = totalPrice;
    storage = totalPrice;
  });
});

modalForm.onclick = function() {
    alert(storage);
}