WooCommerce: Price without Tax as Price Suffix

function show_price_without_tax($price_html, $product)
{
	if (is_product() && wc_prices_include_tax())
		return sprintf(__('%1$s', 'woocommerce'), wc_price(wc_get_price_excluding_tax($product), array('ex_tax_label' => true)));

	return $price_html;
}
add_filter('woocommerce_get_price_suffix', 'show_price_without_tax', 999, 2);

Source