I was reading through the djed and magics and was wondering what was the more likely cause of differences in magical aptitude between people. I assume it is a combination of the following, but was wondering if someone could give me more insight into the idea. Despite equivalent practice I assume one individual will be naturally more talented than another with magic. Is this due to differing levels of djed within their bodies or an innate difference in their ability to use equivalent amounts of djed. I know that with training one can become a more efficient djed user, but this question refers to the differences between two equivalently leveled magic users differences.
On a side note: In Zinrah there are slaves to be had but no costs are listed. Besides paying for their living expenses what would be an accurate cost? I saw the slaves in the price list that cost approximately 100gm for a basic humanoid adult but was wondering whether Zinrah would have more expensive slave because it is so remote or whether it would have less expensive slaves because torture is such a common part of their culture (in this case, buying time with a slave rather than the slave itself to take home).
Thanks for your time guys!