People should not value love more than life
"I long to die/If what thou speakst not of remedy." (Act 4, Scene 1. p1074, lines 73-74; Juliet to Friar Laurence; she wants his help to escape marrying Paris).
"Romeo, I come! this do I drink to thee." (Act 4, Scene 3. p1079, line 60; Juliet to Romeo, from a far distance, because she's drinking the sleeping potion).
"Here's to my love! (drinks.) O true apothecary! Thy drugs are quick. Thus with a kiss I die." (Act 5, Scene 3. p1097, lines 122-133; Romeo to Juliet/himself because he is dying).
Romeo and Juliet both obviously valued love over life: Juliet would rather die than be stripped of her love for Romeo, so Friar Laurence is rushed into making a plan for them to be together and "save" Juliet's life. The consequence is that this begins the spiral of events that result in the two's deaths. If Juliet hadn't threatened to kill herself if she couldn't have her love, the Friar would've had time to make a better/safer plan. Romeo's values were plainly conveyed by his line "Here's to my love!" as he drinks the poison that will kill him. This is a prime example of why people should not value love over life because if Juliet had not come to the Friar in a suicidal fit and in turn Romeo had decided not to kill himself the starcrossed lovers would've been able to be together.
Act 3, Scene 1
"And for that offense/Immediately we do exile him hence." (p1051, lines 202-203; The Prince to the people of Verona because Romeo killed Tybalt).
Romeo values his love for Mercutio over Tybalt's life because he is willing to kill Tybalt solely because he killed Mercutio. The consequence of his actions was his exile (and therefore, indirectly, his and Juliet's deaths).
Act 3, Scene 3
Romeo is ready to kill himself because his name brings Juliet (his love) sorrow, but in reality that would only cause her more pain and Romeo's love is blinding him of that fact.
Act 5, Scene 3
Paris sees Romeo as the cause for Juliet's death, so he feels that his love for Juliet is justification to kill Romeo. This results in his death.