As of Sales Pack v2.0.
Suppliers can be accessed at Products > the top right menu > Suppliers or Purchase Orders > the top right menu > Suppliers. It's also possible add the Suppliers navbar tab.
Access to Suppliers is controlled by Roles.
It's possible to specify Supplier Prices for specific products. There can be multiple prices for the same product: for specific date range or quantity.
Whenever a product is added to a Purchase Order, the system will look up the price in the associated Supplier.