Often customers will try an negotiate a lower than retail price and you will need a solution to be able to address this scenario for custom pricing.
In PSA Projects there a certain restrictions which will mean you can only use one or two Quote Lines associated as well as resources in order to provide estimations. However you will also need to consider resource costs before quoting a price without creating a loss by allowing to easily remove or find alternative resources to reduce the cost and without creating a loss for your company.
This will allow you to be allow more flexible in finding and adding cheaper resources when building quotations and by using Custom Pricing Dimensions you can overcome many of the limitations.
Fixed Time Projects entails risk is with Resource Provider but by offering Projects billed by Time and Materials there is less risk and allows to offer more discounts in such scenarios.