$(document).ready(function () {
    $("input[type=radio]").click(function () {
        $(this).closest('form').find("input[type=text]").val(this.value);
    });
});

input[type=radio][checked=checked]{background:#000}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form action="hello.php" name="form01" method="post">
    <input type="hidden" name="productid" value="01" />
    <input type="radio" name="price" value="1000" checked="checked">1000
    <input type="radio" name="price" value="2000">2000
    <input type="text" id="it1" name="pricevalue" value="1000">
</form>
<form action="hello.php" name="form02" method="post">
    <input type="hidden" name="productid" value="02" />
    <input type="radio" name="price" value="6000" checked="checked">6000
    <input type="radio" name="price" value="2400">2400
    <input type="text" id="it2" name="pricevalue" value="6000">
</form>
<form action="hello.php" name="form03" method="post">
    <input type="hidden" name="productid" value="03" />
    <input type="radio" name="price" value="500" checked="checked">500
    <input type="radio" name="price" value="700">700
    <input type="text" id="it3" name="pricevalue" value="500">
</form>