I haven't read the entire thread in detail, but to me the bit that's missing is the full 360-degree view of the Economics, i.e. I see lots of discussion on the expected earnings / profits affecting the price, but you also have to factor in the Supply side, i.e. how much does it cost to get a new slave, and hence if the price is too high then every adventurer will want to go out and get some new slaves to sell for huge profits, and hence the price will be driven down.
Basic supply and demand - the price is whatever balances the demand vs supply; Elasticity.
For example I imagine it cost a lot of money to get an initial supply of slaves from Africa to America; I'm not sure if it ever became illegal or just more difficult to get more later on, but there's food for thought in terms of the cost and time required for breeding vs re-supply. If your world is crawling with adventurer types and/or technology that makes getting new slaves relatively easy, I'd say that will drive prices down a lot; if there's very few people who can actually obtain new slaves, then higher prices can be sustained.
Basic supply and demand - the price is whatever balances the demand vs supply; Elasticity.
For example I imagine it cost a lot of money to get an initial supply of slaves from Africa to America; I'm not sure if it ever became illegal or just more difficult to get more later on, but there's food for thought in terms of the cost and time required for breeding vs re-supply. If your world is crawling with adventurer types and/or technology that makes getting new slaves relatively easy, I'd say that will drive prices down a lot; if there's very few people who can actually obtain new slaves, then higher prices can be sustained.