When evaluating a business project, a textbook recipe is to take incremental income from the project and subtract the incremental costs -- including opportunity costs -- to arrive at the incremental result*. When choosing among competing projects, one compares the incremental results and chooses the project with the highest one, ceteris paribus.
I am a little bothered by the treatment of opportunity costs here. I also think there is a conceptually simpler alternative**. I wonder what, if anything, could go wrong if we first evaluated each possible project (in the broadest possible sense so as to include everything the business owner could do with his/her resources***) without subtracting opportunity costs and then compared the results across projects. Would that possibly yield a different result?
*Incremental result and such is probably not the standard terminology. Feel free to suggest how to rephrase in standard terms.
**What is conceptually simple vs. difficult can of course be debated.
***This has been edited in response to the example of @1muflon1. I count becoming an accountant as one of the projects under consideration. If this thought/project is in our universe, it has to be evaluated alongside all the other alternative projects.