How we cite our quotes: (Act.Scene.Line)
Quote #4
Brother, she is not worth what she doth cost The keeping. (2.2.51-52)
The Trojan princes spend a whole lot of time arguing about whether or not Helen has any "value" to them and whether or not she's "worth" all the lives that have been sacrificed to the war. In fact, Helen is portrayed as a commodity throughout the play, as is Cressida, who is actually traded to the Greeks as if she's nothing more than a piece of merchandise that can be bought, sold, or traded.
Quote #5
She is the theme of honor and renown, A spur to valiant and magnanimous deeds, Whose present courage may beat down our foes, And fame in time to come canonize us. (2.2.199-202)
After a lengthy argument about whether or not Helen is "worth" fighting the Trojan War for, Troilus announces that, Helen is just a "theme of honor and renown." In other words, Helen is merely an excuse for the men to fight so they can perform "valiant and magnanimous deeds" and earn serious props on the battlefield. Basically, Helen is beside the point.
Quote #6
[...] all the argument is a cuckold and a whore; a good quarrel to draw emulous factions and bleed to death upon. (2.3.70-73)
We hear some version of this offensive argument over and over again throughout the play. According to Thersites, the Trojan War is being fought over nothing more than a "whore." It's not a noble war, like, say, a land grab or a colonizing attempt.