Competitive advantage theory has been around since the ‘80’s. A simplistic way of defining it is “what can I do better than the competition?”
Which has led to a work of specialisation. People doing what they are good at and outsourcing what they aren’t as good at. We don’t all make our own clothes, because there are people who can do it better than us.
Which leads to the question. When should you outsource a task?
The answer can be boiled down to one simple question. Is it a task that has economies of scale?
If so, then we can dive into whether someone is specialising in it and doing a better job than you can do internally. ‘Better’ might mean lower cost, higher return, more time efficient, larger reach, lower risk, or more consistent.
Note that the emphasis here is on ‘better’. Their economies of scale needs to outperform your personal efforts to generate a return on the additional cost.
Hopefully your accountant is outperforming any job you could otherwise do on your taxes, and they are doing better than the rest of their competition.
As should your marketing. Is a professional finding opportunities and efficiencies that you aren’t?