| Quote #1
And of a carat of this quantity,
Diamonds are a man's best friend. They're not just shiny; they can get you out of serious trouble. In fact, the exact situation Barabas describes here happens at the end of the play: Ferneze refuses to return Calymath (a 'captive king', of sorts) to his father, the Turkish Sultan, unless the Sultan forks over the money for the restoration of Malta.
| Quote #2
Who hateth me but for my happiness?
On Malta, people give you kudos for being rich, not righteous. If Jews are the ones with the money, then Judaism is the way to go, right? Well…not quite. By the end of the first act it's clear that Christians don't dig poverty any more than the Jews. The allocation of wealth may depend more upon whether you're part of the majority part than on your religion.
| Quote #3
Honour is bought with blood and not with gold. (2.2.56)
Bosco says this, but—spoiler alert—it's a lie. A big, fat, lie. First of all, as Barabas has helpfully pointed out, in Malta people are honored precisely for their wealth. In addition, Bosco isn't offering to help Ferneze fight the Turks because it's honorable, he's doing it so he can sell his slave on Malta and get some gold for himself.