The notion that we can ignore - many times willfully - the microeconomics of decision making is common in some development domains. Any project driven paradigm has many elements, each interacting with each in random ways, in nonlinear ways, in ways we may not be able to even understand when the maturity of the organization is not yet developed to a level needed to manage in the presence of uncertainty.
So When We Say Project What Do We Mean?
The term project has an official meaning in many domains. Work that has a finite duration is a good start. But then what is finite? Work that makes a change to an external condition. But what does change mean, and what is external. In most definitions, operations and maintenance are not usually budgeted as projects. There are accounting rules the describe projects as well. Once we land on an operational definition of the project, here's a notional picture of the range of projects.
My favorite questionable conjecture is that we can make decisions about the spending of other peoples money without estimating the outcomes for that decisions. Making decisions about an uncertain future is the basis of Microeconomics.
One framework for making decisions in the presence of uncertainty is Organizational Governance. Without establishing a governance framework, ranging from one like that below, to No governance, just DO IT, it's difficult to have a meaningful conversation about the applicability of any project management process.
So when we hear a new and possibly counter intuitive suggestion, start by asking In What Governance Model Do You Think This Idea Might Be Applicable?