Most of us have "enjoyed" the experience of making multiple trips to the hardware store when attempting to install what often seems to be the simplest of tasks. After this task consumes most of the day, including all kinds of time that was not planned, we rock back and ask ourselves, "why didn't I just hire a professional?".
The amateur in the scenario above most likely just spent twice or more in time and money, than if a professional would have been hired. This reminds me of a quote from the famous oil well firefighter, Paul "Red" Adair. He would tell folks, "If you think it’s expensive to hire a professional……wait until you hire an amateur!". Candidly, he's right.