I think that Feynman was talking about preparing a freshman-level lecture for Caltech-standard freshmen, but maybe you have somebody else in mind.
If the person you are explaining your project to is not interested in the technical side, presumably under the rather confused but popular theory that technical aspects are not relevant to technology ventures, you'll not be making headway. It's much better to just make up some dollar numbers and run with that.
The average person can understand anything ... at some level. Being able to match that level is positive evidence (but not proof) of competence.
Duality: Being unable to match that level is positive evidence (but not proof) of incompetence.