Very good point with the math. However with super expensive markets, doesn't their commission then match their increased cost of living to be working there?
that can be used to justify almost any level of commission including fixed fee rate. ultimately its modulated by increase number of realtors coming into the market. the core amount of work needed to buy/sell a house is not that much and can be effectively segmented to specialized (low-cost) individuals like Redfin is trying to do. you could also argue that in hot markets like sf-bayarea homes sell themselves so the workload on realtors is not so much, which means they can sell more houses to make up for 'lost' commission like rest of america.
the problem is that even if a realtor wants to reduce his commission, he has no control over the other party and they'll want to have full 3%. this minimizes the incentive to disrupt the process though in super expensive markets it may still make sense.
