WooCommerce - Create a cost price field for simple products

functions.php

add_action('woocommerce_product_options_pricing','custom_cost_price');
function custom_cost_price() {
  woocommerce_wp_text_input( array( 'id' => '_cost_price', 'class' => 'wc_input_price short', 'label' => __( 'Cost Price', 'woocommerce' ) . 	' ('.get_woocommerce_currency_symbol().')', 'type' => 'number', 'custom_attributes' => array(
					'step' 	=> 'any',
					'min'	=> '0'
				) ) );
}

add_action('woocommerce_process_product_meta_simple', 'save_custom_cost_price');
function save_custom_cost_price($post_id) {
	global $wpdb, $woocommerce, $woocommerce_errors;
	update_post_meta( $post_id, '_cost_price', stripslashes( $_POST['_cost_price'] ) );
}