Yes, you're right: gladiators were an investment and no one wanted to waste his money. Usually gladiators were professionists and didn't die fighting; the public enjoyed the fight but death was something that involved mostly who was condemned to death (and for it there was a special "show", like the damnatio ad bestias). Gladiators could be men condemned to death too, but it was not always like this (see above).
So in the cities of average size, gladiators could hope to survive for some years, even if obviuosly their job was dangerous and the chances to die in the fight were high.
I wrote about medium-sized cities, like Pompei or Capua, because Rome was different: even there gladiators not always died during the fight, but the entrepreneurs were so rich that they could afford more losses, so often fightings in the capital were bloodier.
Anther misconception is that all the gladiators were slaves or prisoners of war: free men could become gladiators but this job was really infamous. There was a law that listed jobs and behaviours which were not allowed for candidates to the elections (lex Iulia Municipalis) and among them there was gladiators job. Just very poor people decided to became one of them.
Anyway, sometimes free men did it because they were attracted by the celebrity gladiators could reach. This looks like a contradiction, but gladiators were equally despised and loved; especially common people loved them and on the walls of Pompeii there are some declarations of love from women to their favourite gladiator.
Finally, gladiators could become very very rich and gain freedom.