It is a complicated task to determine whether your price is fair. It depends on what the scope of your project is and your objective.
Coordinating with each trade/group yourself will save you money as opposed to letting someone else handle that for you. Prices are determined by material, labor and administration costs which can be marked up when you put the job of coordinating in someone else’s hands.
Less middlemen, lower price.
Professional, well run companies can save costs along the way and may pass the savings to you.
Always do comparison shopping, but make sure when you compare, you compare apples to apples. You need to go through a detailed technical analysis, especially when more material and labor is involved. It can be time consuming but it well worth it and it may save you thousands of dollars.