JSFiddle - React, Tailwind, and code Playground

HTML

<div class="item-price-block">
    <div>
        <div id="totalCount">0</div>
        <div class="associated-items">
            <h5>Список</h5>
            <ul id="associatedList">
                <li>
                    <div class="associated-name">Дверной короб</div>
                    <div class="associated-price">750 грн</div>
                    <div class="number">
                        <span class="minus">-</span>
                        <input id="8632" name="quantity" type="text" value="0" />
                        <span class="plus">+</span>
                    </div>
                </li>
                <li>
                    <div class="associated-name">Комплект наличников</div>
                    <div class="associated-price">300 грн</div>
                    <div class="number">
                        <span class="minus">-</span>
                        <input id="8633" name="quantity" type="text" value="0" />
                        <span class="plus">+</span>
                    </div>
                </li>
                <li>
                    <div class="associated-name">Комплект доборной доски (расширитель)</div>
                    <div class="associated-price">350 грн</div>
                    <div class="number">
                        <span class="minus">-</span>
                        <input id="8634" name="quantity" type="text" value="0" />
                        <span class="plus">+</span>
                    </div>
                </li>
                <li>
                    <div class="associated-name">Установка межкомнатной двери</div>
                    <div class="associated-price">1 000 грн</div>
                    <div class="number">
                        <span class="minus">-</span>
                        <input id="3000" name="quantity" type="text" value="0" />
                        <span class="plus">+</span>
                    </div>
                </li>
            </ul>
        </div>
   ...

JavaScript

function changeTotalPlus (event){
        var price =  parseInt(this.event.target.parentNode.previousElementSibling.textContent.replace(/\s+/g, ''));
        var quantity = parseInt(this.event.target.parentNode.querySelector('input').value);
        var totalDiv = parseInt(document.getElementById('totalCount').textContent);
        var sum = totalDiv + (price * quantity);
        var total = sum++;
        document.getElementById('totalCount').textContent = total;
    }