In Romeo and Juliet what does the prince means by this sentence: "All are punished " ... ((in the last pages))Act 5, Scene 3, line 315 .

I would add to the previous two posts that in these
lines, the Prince refers not only to the Capulets and Montagues, but to HIMSELF as
well:

"And I, for winking at your discords too,/ Have lost
a brace of kinsmen."

The kinsmen here are Mercutio and
Paris (both were related to him).  The Prince implies that he has lost them for having
failed to resolve the conflict earlier.  He suggests that he was too "soft", and that if
he had been more firm, perhaps the feud would not have ended in
tragedy.