For now, QuickBooks Online doesn't have an option to set up price rule for customers. As a workaround, you can create items such as non-inventory, inventory, bundle, and services instead and set up a category for them.
You may consider deploying a B2B ecommerce for your case. There is a New Zealand company (and also has an office in Australia, US and UK) provides an inventory management with built-in B2B ecommerce. It integrates with various business apps including QBO. It automatically show contract pricing of selected products for particular key customers. It lets you create multiple price lists and promotions for different customer groups. PM me for details.