JSFiddle - React, Tailwind, and code Playground

HTML

<input class="span4 input-big" id="dare_price" name="price" size="30" type="text" onChange="updatePrice()" />
<input class="span4 input-big" id="total_price_amount" readonly="readonly" value=""/>

JavaScript

function updatePrice()
    {
        var price = $("#dare_price").val();
        var total = (parseFloat(price) + 1) * 1.05;
        console.log(total);
        $("#total_price_amount").val(total);
    }