Real Time Calculations?

I have searched through all of SOF and couldn't find any topic that matches my problem. I have written an HTML form that I will use PHP to process later, but I have some options in

Solution 1:

This should work how you want. Also, does not require jQuery.

function doMath() {
    var basePrice = 15;
    var baseModel = 0;
    var customModel = 5;
    var modelTotal;
    if (document.querySelector('input[name="FIELD6"]:checked').value == "Normal Model") {
        modelTotal = basePrice + customModel;
    }

    if (document.querySelector('input[name="FIELD6"]:checked').value == "Workshop Model") {
        modelTotal = basePrice + baseModel;
    }
    console.log(modelTotal);
    document.getElementById('total').innerHTML = '<span style="color:black">Total Price:' + modelTotal + '</span>';
}

<label for="FIELD6">Model Type:</label>
<br>
<input type="radio" id="basemodel" name="FIELD6" value="Normal Model" onclick="doMath()" />Normal Model
<br>
<input type="radio" id="workshopmodel" name="FIELD6" value="Workshop Model" onclick="doMath()" />Workshop Model
<div id="total"></div>

Solution 2:

Here is a working example of what I think you are asking for.

<label for="FIELD6">Model Type:</label><br>
<input type="radio" id="basemodel" name="FIELD6" value="Normal Model"  checked  onclick="doMath(this)" />Normal Model<br>
<input type="radio" id="workshopmodel" name="FIELD6" value="Workshop Model" onclick="doMath(this)" data-clicked="no" />Workshop Model
<p id="total"></p>

<script type="text/javascript">
    function doMath(ele) {
        var total = 15;
        if($(ele).attr('id') === 'workshopmodel') {
            total += 5;
        }
        $("#total").html('<font color="black">Total Price:</font><font color="#09ff00">' +  total);
    }
</script>