JSFiddle - React, Tailwind, and code Playground

HTML

<div class="price">

<table width="100%" border="0" cellpadding="0" cellspacing="0">
<tr>
    <td width="190"><span class="price-text">Цена для вас в Дисконте:</span></td>
    <td></td>
    <td></td>
</tr>
<tr><td colspan="3" height="10"></td></tr>
<tr>
    <td><nobr><span class="price-red"><b>299®</b></span></nobr></td>
    <td></td>
    <td></td>
</tr>
</table>
</div>

CSS

.price-red{
    color:red;
    font-size:60px;
}

JavaScript

$('span.price-red:contains("®")').html(function () {
    return this.innerHTML.replace("®", "<span style='font-size:40px;background:red'>®</span>")
});