"Lower" with respect to ?... Each of them starts by receiving what they would have gotten working alone, so C will anyway always get at least 3. Whether he receives more than that and how much more depends on how successful he is at cooperating. For instance, with B, the team is not great as it produces 0 added value. With A, the total added value is 2.5 so C receives 1.25. For A+B+C, as long as C gets at least 1.26 (instead of 4/3=1.33) it will be in his own interest to work in the trio. That 0.07 allow A and B to go from 1.33 to 1.36-1.37 for instance. Still not 1.5 though, but a bit better