add_shortcode( 'item_price', 'func_item_price' );
/**
 * Register [item_price] shortcode to return the value of `item_price` custom field.
 *
 * @return int the item price.
 */
function func_item_price() {
	$item_price = get_post_meta( get_the_ID(), 'item_price', true );

	if ( $item_price ) {
		return $item_price;
	}
}