1. 135 hours is a LOT of time to invest for even tens of thousands of dollars return. I could build and market a side project or two in that time, which could have potential for significantly higher return.
2. To recoup that return, I have to take a big risk, using a highly inexperienced agent (me) in a huge dollar transaction where everyone I speak with will have much more experience.
3. Worst decisioning -- if I am my own agent, I'm not in a good environment for optimal decision making.
There are other reasons outside the scope of your question (some people prefer lower touch investments), but those are a few.
The math just doesn't work out, if you get to the point you are doing that many deals, just hire a broker for your business.
Getting access to the MLS isn't that hard. And finding a good agent/broker to work with is very doable as they want to work with investors since it is a source of recurring income usually for them.
That all said, I am always interested in other peoples approach to minimize transaction fees, but most investors I know in real estate use this approach as it just works and minimizes liability.
I do agree in reference to fees from brokers etc, but if you do some deals you will find someone you can work with and honestly at that point they'll work with you on the fees and you won't care as much either because they'll take the liability so their fees are fair.