Well, the previous answers are good, but I will show you another way to say it.
In Colombia We don't say: Merece la pena. We say: Vale la pena. (Verb in spanish: Valer):
So, in past tense we say "Valió la pena" and in future tense we say "Valdrá la pena"
Is not common to conjugate this verb for a person, but I will show you the conjugation:
Conjugación del verbo Valer:
Yo valgo
Tu vales
El/Ella vale
Ellos/Ellas valen
Ustedes valen
Nosotros valemos