How we cite our quotes:
PROMETHEUS. I am in this wretchedness, yoked in these constraining bonds, because I gave privileges to mortals: I hunted for, and stole, a source of fire, putting it into a fennel-stalk, and it has shown itself to be mortals' great resource and their teacher in every skill. Such is the offence for which I am paying this penalty, pinned in these bonds under an open sky. (101-113)
If Prometheus knew in advance what would happen, that implies that he chose what would happen—in other words, that he's deliberately sacrificed himself. So stop whining, already! J/k, dude, we love you.
PROMETHEUS. It's very easy for someone who is standing safely out of trouble to advise and rebuke someone who is in trouble. I knew all that, all along. I did the wrong thing intentionally, intentionally, I won't deny it: by helping mortals, I brought trouble on myself. But I certainly never thought I would have a punishment anything like this, left to wither on these elevated rocks, my lot cast on this deserted, neighbourless crag. Now stop lamenting my present woes: descend to the ground and hear of my future fortunes, so that you will know it all to the end. Do as I ask, do as I ask. (257-274)
Okay, now Prometheus is saying he didn't actually know what his punishment would be like. So would he have chosen differently if he knew what he knows now? And does his theft of fire become less of a sacrifice if he didn't have clear knowledge of what was going to happen to him?
IO. Finally a clear word came to Inachus, plainly telling and enjoining him to thrust me out of my house and my native place, to wander unprotected on the furthest confines of the land; and that if he refused, a fiery thunderbolt would come from Zeus that would annihilate the entire family. Persuaded by these oracles of Loxias, he expelled me and shut me out of his house—as reluctant to do it as I was to go: the bridle of Zeus compelled him against his will to act thus. (655-672)
Hey, Io is a sacrifice, too. But their situations aren't exactly identical: Prometheus sacrifices himself; Io is sacrificed by her dad. That's a pretty big difference.