It's easy to add content to your site using a little javascript.

To display "FREE SHIPPING" under the product's price just copy and paste the following code into the Custom HTML <head> field within your Website Configuration.

<script type="text/javascript">
    $(document).ready(function(){
        $("#ctl00_MainContentPlaceHolder_YourPriceLabel").after("<br/>FREE SHIPPING");
    });
</script>

Only Show Free Shipping When the Price is Over $XXX.XX

You may also use javascript to control when the message is displayed. Using the code below the "FREE SHIPPING" message will only be shown when the product's price is equal to or greater than the amount you specify in the code. Make sure you change the ENTER_YOUR_PRICE_HERE variable to an actual price. No dollar signs!

<script type="text/javascript">
$(document).ready(function() {
        var yourPriceLabel = $("#ctl00_MainContentPlaceHolder_YourPriceLabel");
        if (yourPriceLabel.length) {
                var itemPrice = parseFloat(yourPriceLabel.text().replace(/[^\d\.]+/g,""));
                console.log(itemPrice);
                if (itemPrice != NaN) {
                        // Replace "ENTER_YOUR_PRICE_HERE" with the starting price you want free shipping displayed. E.g. 150.00 or 123.45. Do NOT enter a dollar sign!
                        if (itemPrice >= 200) {
                                console.log("Item is eligible for free shipping");
                                // Show a message under the price. You may change "FREE SHIPPING" to whatever you like.
                                yourPriceLabel.after("<br/>FREE SHIPPING");
                        }
                }
        }
});
</script>

Please note, you may change <br />FREE SHIPPING in the code to any valid HTML (images, links, etc.).