I have purchased four houses and sold three. All of the realtors I worked with earned their money, big time.
The price of a house is an emotional number, not a scientific number. Zillow computes semi-random numbers.
Buying: The realtor knows the neighborhoods, how the prices are changing, advantages and disadvantages, what kind of people live there, new construction coming, possible flooding, airport noise, etc. The realtor learns what you want in a house, neighborhood and school district, and tries to find the best fit. The realtor knows contractors, painters, inspectors, plumbers, roofers,decorators, gardeners, who can fix problems. You have to make trade offs. The realtor knows banks and mortgage companies and can find good deals that you would qualify for, and can explain terms and rates.
Selling: The realtor knows the neighborhoods, how the prices are changing, what people are looking for, what to change in your house, how much to spend to help it sell. The realtor knows contractors, painters, inspectors, plumbers, roofers,decorators, gardeners, who can fix problems.
On our last move, we were able to buy the new house, and then sell the old house. They were 120 miles apart, so we usually were not there at the empty house. On the new house, we had to fix dry rot under the bathrooms, completely paint the interior, and fix some floors. The realtor oversaw the workers. Weird feature: hot air balloons fly over our house.
On the old house, about 50 years old, we had the inspections, fixed the roof, totally repainted the interior and the exterior, replaced all of the carpet, added new plants in the front, replaced the kitchen appliances, replaced all of the door handles and hinges, and rented pretty furniture for all of the rooms. The realtor oversaw all of the work. Got eight bids in one week, all over asking price.
So yes, both realtors worked their butts off, their experience and advice and nudging were worth every penny. Both worked for real estate firms, so they received only part of the commission.