There's no inherent reason that investment bankers or real estate brokers should be paid dramatically more because a deal is larger when serving as market makers. While the value of the match is higher, the function they serve is the same. Technology seems well placed to help the buyers and sellers find each other for a fixed fee.
If we suppose that match making could be done for a fixed fee, would brokers still be able to demand commission based compensation? I think the answer is no. The advice they give based on domain expertise would likely be compensated at an hourly rate similar to lawyers and consultants.
It'll be a long time until this is the case, but when computers are able to effectively source deals, I suspect that we'll see transaction fees transition away from being commission based.