YITH WooCommerce Role Based Prices lets you change the price of the products in your store dynamically, increasing or decreasing it based on the role the user has.
The integration between this plugin and YITH Product Add-Ons allows changing the base product price according to the role of your users while keeping the add-on prices unchanged for all users.
All you have to do is to activate both plugins from the Plugins menu and then start configuring your role-based prices rules from this page, which apply to the product’s regular price.
After that, you can start configuring your add-ons to let your users have custom options and, if you want to, charge a fee for each selected add-on.
The product price will be calculated starting from their role-based price. The add-on prices will be the same for every user and will add to the product role-based price.
You can learn more about how to configure the add-ons on this page.

If you want to learn more about how to properly set up YITH Role Based Prices, please, refer to the plugin official documentation.