function custom_get_price_html_from_to( $price, $product ) {
	$from = $product->regular_price;
	$to = $product->get_price();

	if ( $product->is_on_sale() )
		return ( ( is_numeric( $from ) ) ? woocommerce_price( $from ) : $from ) . ' <ins>' . ( ( is_numeric( $to ) ) ? woocommerce_price( $to ) : $to ) . '</ins>';

	return '<del>' . ( ( is_numeric( $from ) ) ? woocommerce_price( $from ) : $from ) . '</del> <ins>' . ( ( is_numeric( $to ) ) ? woocommerce_price( $to ) : $to ) . '</ins>';
}

add_filter( 'woocommerce_free_sale_price_html', 'custom_get_price_html_from_to', 10, 2 );
add_filter( 'woocommerce_sale_price_html', 'custom_get_price_html_from_to', 10, 2 );
add_filter( 'woocommerce_variable_free_sale_price_html', 'custom_get_price_html_from_to', 10, 2 );
add_filter( 'woocommerce_variable_sale_price_html', 'custom_get_price_html_from_to', 10, 2 );