Did you know that with WooCommerce MSRP Pricing you can add the manufacturer suggested retail price to your products?
If not, well you should definitely try it!
This extension lets you add the suggested retail price for all the products in your store, but that price only shows in the front end of the site, while you probably also need it in the back-end, expecially in the order admin pages.
You can add it to the order items table with some custom code.
Open your functions.php file located in wp-content/themes/your-theme-name/ and add this code at the end of the file:
The code will add the column MSRP to your order items table showing the MSRP price for all the products.
It will look like this: