Clarification of iterated prisoners dilemma
The payoff depends entirely on how you set the game up. Here's one example of the case where $2R \leq T + S$:

                                  Player B
                           Cooperate  |    Defect
Player     Cooperate        (1, 1)    |  (-2, 100)
A          Defect          (100, -2)  |  (-1, -1)


Here, $R = 1$, $T = 100$, and $S = -1$, and $2R &lt; T + S$.

Edit: To add a bit more value to the answer... any game could be played repeatedly (and thus is "iterable" in that sense.) However, my understanding is that the Wikipedia page writer means that for (Cooperate, Cooperate) to be sustained, you at least need this condition to be true.