JSFiddle - React, Tailwind, and code Playground
by ipr101
HTML
<table border="1">
<tr>
<td class="mcount_el">2</td>
<td class="mprice_el">544,33</td>
<td class="mcost_el">0</td>
</tr>
<tr>
<td class="mcount_el">3,9</td>
<td class="mprice_el">460,00</td>
<td class="mcost_el">0</td>
</tr>
</table>
JavaScript
var count=0;
var price=0;
$('tr').each(function(){
count=parseFloat($(this).find('td.mcount_el').text().replace(",","."));
price=parseFloat($(this).find('td.mprice_el').text().replace(",","."));
$(this).find('td.mcost_el').html(count*price);
});