1) Yeah, how many accounts does matter. A day has 24 hours. Your setup requires manual intervention for a lot of things. Again, it's not sustainable, TRY IT and then we can talk like grown-ups.
2) Every single multibotter has gone through that point (market controlling) before going harder. You'd better don't think that you have unique knowledge of the Ins and out of the wow economy, because it's not unique. We've all controlled realms and then tried to move to a a bigger scale.
What you said about finding the market completely proves the point. Niche markets can't hold beyond a couple of days of farming mats. Then you have to be replenishing the Ah, and you'll find yourself controlling the market in a good with a low demand, and your banks full.
Actually, you need to find something that doesn't require manual intervention, or at least is reduced to under 15 minutes a day. Do you wonder why you still see dungeon bots when it's such a low profit? Because that's sustainable. Exactly what we are talking about.
3) You are indeed botting for peanuts, mate. And you know it. That's why I'm encouraging you to try to expand beyond your 3-4 accounts- you'll realize how all you ideas are impossible in the medium - bigger scale, and why every single person that reads this and has managed even a smaller farm with 10+ bots perfectly knows it.
Feel free to hit me in PM to talk about this, if you want. I don't wanna hijack this thread, and it seems we are doing so.