JSFiddle - React, Tailwind, and code Playground
by Qwerty_Wasd
HTML
<div class="price_byn">
<div class="price">
2<b class="f_normal">р.</b>
<span class="cent">49<b class="f_normal">к.</b></span>
<div class="old_price">
3
<b class="f_normal">р.</b>
<span class="cent">31<b class="f_normal">к.</b></span>
</div>
</div>
<small class="kg">за 1 шт</small>
</div>
JavaScript
Array.from(document.querySelectorAll("div.price_byn div.price *:not(.old_price)")).map((e)=>console.log(e.textContent))