You're right, that the majority of the work of a 10 million dollar house is customer acquisition. And this isn't true of a 100k condo.
But this was my point, 3% of a 100k home is close to the competitive market price. But 3% of a 10 million dollar home is pretty far away from the competitive market price.
100x the comission might have 100x the competition. As a seller of the house, you pay more but you also get better agents.
The most successful agents I know close houses twice as fast as other agents. But they close them twice as fast as other agents because they're listing them under market value.
My wife was a real estate agent for 5 years but she got out of it because all of the most successful agents she met were more successful in ways that hurt the client not helped them.
Examples - convincing their clients to settle for homes quickly, convincing clients to list their house less than market value, weeding out easy clients.
It is what it is. RE is not a perfect market because goods really cant be commoditized.
I reiterate my point with one more argument: the average income of a realtor is very low: they make very little money. The number of active realtors is almost perfectly correlated with house prices: that means a highly competitive , and thus relatively efficient, system.