“Gladiatorial Combat: The Rules of Engagement”, M. J. Carter2006-12 (history)⁠:

Though a dangerous and potentially fatal contest, gladiatorial combat during the Roman Empire was nevertheless bound by recognizable rules and expectations. The contests were fought by expensive professionals and supervised by referees.

But more than this, these combats may also have been governed by an unwritten “code of conduct” enforced by the gladiators themselves: to fight bravely in hope of victory, but not to wound or kill needlessly.

…Yet Urbicus’ anxious exhortation to kill is remarkable because it is almost unparalleled. Of the hundreds of epitaphs surviving from throughout the Roman world, few provide anything like the homicidal declaration made here. If the gladiator’s death is mentioned at all, his opponent is almost never blamed for it; instead blame is assigned to the Fates or even to the deceased’s own choice. Furthermore, several gladiatorial epitaphs present a picture completely at odds with Urbicus’ admonition, for instead of inciting murder, these other gladiators boast of having “saved many” in the arena or of having “hurt no one.”

…If a gladiator fought and came off unharmed, he would have been returned to the lanista and the contract considered fulfilled. But if he were injured or killed, the lease would convert to a sale and the gladiator’s full cost would have to be paid, a sum that might be some 50× higher than the lease price.⁹ A senatus consultum from the time of Marcus Aurelius & Commodus attempted to reduce and control the prices of trained, professional gladiators, who ranged in overall value from as low as 3,000 sesterces to as much as 12–15,000 sesterces. Thus the death of professional, high-ranking gladiators resulted in enormous increases in the costs associated with providing gladiatorial munera.

…Some gladiators compiled large numbers of victories during the course of their career. For example, some gladiators listed in an inscription from Claudiopolis in Bithynia had as many as 65 victories, clearly life-time totals (to the date of the inscription)