Hello and welcome to namePros!
I don't have experience in buying high appraised expired domains in high volume and selling them right away for low profit margins, but I'm used to make business plans and I have an idea of the amount of sales you can expect, and what you're suggesting doesn't sound like a sustainable business.
Though I'm no expert, I'm trying to start a business (nothing to do with domaining) that makes just enough to survive (and a little extra), meaning tight margins, because I'm evolving in a very competitive market, and I'm more expensive than the current competition (I'm differentiating myself through my offerings).