Here are the 16 Unique Combos in X-Men, and the base values for collecting the unique combo:
Beast->Rogue = Beauty & The Beast (425,000)
Beast->Storm = Meteorology (425,000)
Beast->Xavier = Sharp Minds (475,000)
Beast->Wolverine = Savage Animals (325,000)
Cyclops->Rogue = Power Drain (375,000)
Cyclops->Storm = Gold+Blue Leaders (375,000)
Cyclops->Xavier = Teacher's Pet (375,000)
Cyclops->Wolverine = Rivals (325,000)
Iceman->Beast = Angry Yeti (375,000)
Iceman->Xavier = Brain Freeze (375,000)
Storm->Iceman = Hailstorm (375,000)
Xavier->Cyclops->Storm->Wolverine = X-Men Leaders (975,000)
(Storm/Xavier->)Phoenix->Iceman = Fire & Ice (400,000)
(Storm/Xavier->)Phoenix->Wolverine = Unrequited Love (400,000)
(Storm/Xavier->)Phoenix->Cyclops->Wolverine = Lover's Triangle (775,000)
(Storm/Xavier->)Phoenix->Cyclops->Xavier->Iceman->Beast = Original X-Men (1,225,000)
There is a bug? where Phoenix is unable to start a combo, so you have to start with Storm or Xavier to get the combo arrows flashing for any Phoenix combo.
Non-unique and already-collected unique combos start at 125,000. Collecting a unique combo raises the base value of all combos by 50,000.
Collecting 10 Unique Combos lights EB.