Add text to the Price based on conditional in WooCommerce

gistfile1.php

<?php

add_filter( 'woocommerce_get_price_html', 'growdev_custom_price_message', 30, 2 );
/**
 * Add string to
 *
 * @param $price    HTML string
 * @param $product WC_Product object
 * @return string
 */
function growdev_custom_price_message( $price, $product ) {

	//error_log( "price: " . $price );
	//error_log( "product: " . get_class($product) );
	/*
	[11-Nov-2014 16:42:23 UTC] price: <span class="amount">&#36;20.00</span>
	[11-Nov-2014 16:42:23 UTC] product: WC_Product_Simple
	 */

	if ( ! is_admin() ) {
		$s = 59;
		if ( (int) $product->get_regular_price() >= $s ) {

			$free_shipping_text = ' <h4>FREE SHIPPING!</h4>';
			return $price . $free_shipping_text;
		}
	}
	return $price;
}