While Project Operations offers a secure end-to-end solution that includes Sales, Resourcing, Work Delivery, Time Tracking, and Billing, it is not a low-cost option.
This program is a complete ERP system. Integrating Project Operations into a full-service lifecycle is the best practice method (and the approach that gives the maximum return on investment). While this has many advantages, it is not the correct tool for you if you have a limited budget or are not serious about aligning and enhancing your processes.
While the components of this (Power BI, Power Apps, and Project for the Web) are stand-alone programs, they are folded into the full workstream process in Dynamics 365 Project Operations (together with other modules).