JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tbody>
        <tr>
            <th colspan="3">ABITI E INDUMENTI VARI</th>
        </tr>
        <tr>
            <td>Camicia LS PI</td>
            <td>
                <label id="prezzo">€3,50</label>
            </td>
            <td>
                <select name="art1">
                    <option value="">0</option>
                    <option value="1 x Camicia LS PI">1</option>
                    <option value="2 x Camicia LS PI">2</option>
                    <option value="3 x Camicia LS PI">3</option>
                    <option value="4 x Camicia LS PI">4</option>
                    <option value="5 x Camicia LS PI">5</option>
                    <option value="6 x Camicia LS PI">6</option>
                    <option value="7 x Camicia LS PI">7</option>
                    <option value="8 x Camicia LS PI">8</option>
                    <option value="9 x Camicia LS PI">9</option>
                    <option value="10 x Camicia LS PI">10</option>
                </select>
            </td>
        </tr>
        <tr>
            <td>Camicia LS PI</td>
            <td>
                <label id="prezzo">€3,50</label>
            </td>
            <td>
                <select name="art1">
                    <option value="">0</option>
                    <option value="1 x Camicia LS PI">1</option>
                    <option value="2 x Camicia LS PI">2</option>
                    <option value="3 x Camicia LS PI">3</option>
                    <option value="4 x Camicia LS PI">4</option>
                    <option value="5 x Camicia LS PI">5</option>
                    <option value="6 x Camicia LS PI">6</option>
                    <option value="7 x Camicia LS PI">7</option>
                    <option value="8 x Camicia LS PI">8</option>
                    <option value="9 x Camicia LS PI">9</option>
                    <option value="10 x Camicia LS PI">10</option>
                </select>
            </td>
        </tr>
      ...

JavaScript

$('select').on('change', function () {
			    var tot = 0;
			    $('select').each(function () {
			        var q = +$(':selected', this).html();
			        var p = $(this).parent().prev().find('label').html();
			        var i = +p.slice(1).replace(',', '.');
			        tot += i * q;
			    });
			    $('#tot').html(tot);
			});