Is the answer usually to hire an expert?

In the course of most questions here someone will make the suggestion to hire an expert to handle whatever the asker’s dilemma is. Whether that expert is a doctor, lawyer, mechanic, realtor, roofer, salesman, nutritionist, or counselor.

Is that usually the best bet when we have a problem we don’t know how to handle? Should we find someone who does know how to handle it and pay for their advice? What situations do you handle on your own with research and when do you seek someone to help? How do you make the distinction?