The Iron Triangle in Project Management: What You Need to Know https://testpro.io/the-iron-triangle-in-project-management-what-you-need-to-know/

Useful information, please read! 

Imagine one client has requested a project and everything is going smoothly until one thing happens: your team hasn't adjusted the budget the way they thought. They need a thousand dollars more than they expected, and they don't know how to communicate this to the client, which will upset the client. In general, this affects both the scope and time of the project. This will take you longer, as you will have to reorganize the project and methodology again - not to mention a drop in quality if the client refuses to pay more.