Most gladiators were slaves, fyi. Rarely you could make enough money to buy your freedom, but that was hardly unique to being a gladiator. Your other points still stand—it was more attractive than destitute poverty or death.
Also better death as a gladiator than death in the mines.
The article says something quite odd that doesn't make much sense.
> “Hymnis had this tomb made for Palumbos, in memory of her own husband” The image on the stela clearly depicts Palumbos as a murmillo. Although the relatively simple stela isn’t a sign of great wealth, it is evidence that Palumbos and his wife could afford a proper commemoration after his death and have it placed in a prominent location in the city.
I don't see why that is obvious. If the translation "her own husband" is indeed correct it sounds like a woman and her husband (who was not Palumbos) owned slaves (of which Palumbos was one). Her husband died (off in a war maybe)? And when Palumbos also died (honorably in combat like her husband, one presumes) it sounds to me like the woman felt compelled to honor him as a transitory way of honoring her husband (which honor to her husband was also then worthy of inscription).
That is a very different thing than watching your husband go do gladitorial battle in an arena, be killed, and then buy an expensive memorial with all the money he made fighting.
Note: my assumption is that all other context is lost and these words are all we have to go on now. Other evidence I see for this interpretation: "husband" and Palumbos are mentioned separately, when it would have been easier to identify the single subject of the memorial once. "Own" implies a necessary distinction, and while a stela may not have been a sign of great wealth a prominent location for it suggests much more money than a mundane one.