Exclude custom fields from multipliers calculation

I am using this pluging alongside with the Product Addons for WooCommerce.

Product Addons basically creates custom fields that can have their own prices assigned.

The problem is your plugin applies the discounts to everything. If my product costs 100 €, and the price for optional custom field is 10 €, and I am browsing as an user role with multiplier set to 0.9, I need to see the product price of 90 €, while the custom field price remains the same – 10 €. Instead, I am currently seeing 9 € price for the custom field.

The Addons plugin has an option to “exclude the fields from discount calculations”, but it only works with native WC coupons. Is there any way to exclude calculation for these custom fields on your side?

Thank you.