(Exodus 21:32) addresses the case of an ox that gores a bondservant: "If the ox gore a man-servant or a maid-servant." The Mekhilta explains that bondservants were already included in the general rule of "and it kill a man or a woman." So why mention them separately?
The Torah singled them out to apply both lenient and severe special rules that differ from the general case. On the lenient side: if the bondservant was worth a hundred maneh (a very large sum), the owner of the ox still pays only thirty selaim. The payment is capped, regardless of the bondservant's actual value.
On the severe side: if the bondservant was worth only a single dinar — far less than thirty selaim — the owner of the ox still pays the full thirty selaim. The payment has a floor as well as a ceiling.
This dual application creates a fixed-rate system for bondservant deaths. Unlike the flexible valuation applied to free persons (where the payment reflects the victim's actual worth), the bondservant payment is always thirty silver shekels — no more, no less. The fixed amount standardized the value of every bondservant's life in the eyes of tort law. Whether the servant was a skilled artisan worth a fortune or a field hand worth a pittance, the ox owner's payment was the same. The Torah created a uniform price for a category of person whose actual economic value varied enormously.