How important is it to involve a BA in a project

1) The business analyst understands the client's business goals and future application needs and develops the solution that best meets the client's requirements.
2) The business analyst always dives into the client's domain and performs a detailed analysis of the market and competitors.
3) The business analyst is the link between business and development. The business analyst translates the client's needs and desires from the language of business to the technical language the development team understands.
4) After the business analyst defines and approves all the requirements with the customer, the business analyst provides high-quality structured documentation (Software Requirements Specification).
5) The business analyst accompanies and supports all project phases (from idea initiation to testing&deploying)
6) Involvement of a business analyst can reduce the overall project cost.