AS a Project Manager How to add value to your project? | Project Manager Questions

I am telling you few ideas in my mind that as a project manager how you can add value to project & real customer.
Feel the real need of customers. Don't act as a sales person. Work as consultant. Which can add much more value to them and hence people will trust you and that trust will help you to grow your business.
Prepare a presentation of their relevance in simple way and with few words. Provide the satisfied references.
Another concern: As a project manager How to justify the time & human resource cost to other persons with different skills like Sales Manager? So Idea is divide all tasks in micro tasks and try to explain all these in detail. Try that he becomes a part of the team and able to realize the facts.
Dropping price doesn't make any sense. Because if you do it, you have to do it again & again to sell your product. Instead of that increase your product quality.