JSFiddle - React, Tailwind, and code Playground

HTML

<select name="sel_tlcb" id="sel_tlcb" class="selector" onchange="mostrar(this);">
    <option data-description="35€" value='1000' >&nbsp;&nbsp;1000</option>
    <option data-description="70€" value='2000' >&nbsp;&nbsp;2000</option>;
    <option data-description="100€" value='3000' >&nbsp;&nbsp;3000</option>;
    <option data-description="150€" value='4000' >&nbsp;&nbsp;4000</option>;
    </select>
<div id="Tarifa" class="tarifa"></div>

JavaScript

function mostrar( obj ){
    var container = document.getElementById("Tarifa") ;
    var description = obj[ obj.selectedIndex ].dataset.description;    
    container.innerHTML = " Item seleccionado.. " + description;
}
mostrar(document.getElementById("sel_tlcb"));