Respectfully... I do not think this is a fair comparison.
1) Biblical slavery does not exist anymore. If you want to compare it to a book describing how to construct an IED? There are no materials to make the IED ( no slaves to purchase ). So the manual describing the process has been rendered inert. In this example: the book is harmless.
2) Biblical Slavery is described in legal terms. If you want an apples to apples comparison, consider the modern laws pertaining to divorce. Does the law encourage divorce? Maybe yes, maybe no. Consider the laws pertaining to operating a motor vehicle? Does the law encourage owning a car? Maybe yes, maybe no.
Please consider: how does the law encourage or discourage behavior? Taxes and regulation. Tax credits and less regulation encourage behavior; Increased taxes and increased regulation discourage behavior.
Your entire premise is: if there is a rule, then the behavior is encouraged. If there are more rules, it is certainly encouraged? That's why you are asking for more detail about the particulars of cost and the process of purchasing a slave? To show that the practice is encouraged? That is not true when it comes to law. More rules is not evidence that the behavior is encouraged. More rules means the behavior is discouraged. Each slave was taxed. More slaves more taxes. I already told you that Slave ownership is discouraged, not encouraged.
This is why it doesn't matter if the price of a slave and the process for purchasing them is documented explicitly. Yes, it is probably defined. But it still doesn't show that Biblical Slavery is encouraged. As I have shown, more regulations and taxes discourage the practice. And each slave was taxed.
---------------------------------------------
But none of this matters, right? You are looking for evidence to show that God is immoral. And your evidence is that Slavery is allowed, and if God is moral, then the practice should have been prohibited, right?
My opinion? You cannot judge morality without knowing the end of the story and all the details in the middle.
Look, if and when a religious person makes the claim that their "Bible" reflects a perfect moral system, the concept of biblical slavery is a great argument to refute their claim. It's a slam dunk.
If someone says the God of Abraham is only Love and Puppies and Cinnamon Crackers, the concept of Biblical Slavery is a great argument to refute their claim.
And the converse is also true. If a person wants to claim that the English translation of the First 5 books of the Torah is not a perfect moral system, Biblical Slavery is good evidence to support it. If a person wants to claim that the God of Abraham is not **only** Love, and Champagne, and Rose Petals, then the concept of Biblical Slavery is good evidence to support it.
But, Biblical Slavery is not good supporting evidence to show that God is immoral. No human being can show that God is immoral due to lack of evidence. And that is why none of this really matters. The real claim you are trying to make is that God is immoral. And no one can prove that.