Set individual price per instance

Finally got round to trying this out, and so far seems to do exactly what we need.

A minor suggestion, could the instance order form show a placeholder for the cost when the plan selection is changed. There is a delay in the script retrieving pricing from an external source.
I can partially overcome it with some custom CSS and HTML but would be good if this was implemented properly within the UI:

Whitelabel CSS override:

span.plan-price:empty::before {
    content: 'Calculating cost...';
    display: inline-block;
}

And a little bit of Javascript:

<script>
  $('#tmp-plan-select').on('change', function() {
    $(".plan-price").html("");
  });
</script>