The math here depends entirely on what the “certain rights” Lucius has over Harry are. Were the debt a purely financial issue, saving Hermione would be a no-brainer. Did those rights allow Lucius to realistically cripple Harry’s efforts to fix the world, not saving Hermione would be a no-brainer.
We still don’t know, although the fact that Dumbledore ultimately went along with it suggests that it’s closer to the former than the latter.
The math here depends entirely on what the “certain rights” Lucius has over Harry are. Were the debt a purely financial issue, saving Hermione would be a no-brainer. Did those rights allow Lucius to realistically cripple Harry’s efforts to fix the world, not saving Hermione would be a no-brainer.
We still don’t know, although the fact that Dumbledore ultimately went along with it suggests that it’s closer to the former than the latter.