|When "Supply default opportunity line item values" is enabled the Opportunity Product Sales Price and Quantity fields are indeed made "optional". The word "optional" can sometimes be confusing and in most Salesforce scenarios there are multiple definitions for the term. In this specific scenario "optional" means these fields can now be taken off the page layout. The fields are inherently still required and therefore values must exist within them. They cannot be made un-required. However, this feature allows the fields to be removed from the page layout where they are populated with a default value that requires no User input.