And with Gregtech it takes almost 3 RL weeks to pay itself off.
LOL. One of the point of GT was to make UUM less OP. So I would answer:
1) If you're thinking to each generators in terms of UUM, then you're already lost ^^. Whats the point of mining once you can get everything very easily using UUM ? GT just makes UUM non-breaking the whole mining system of MC.
2) UUM is nerfed by GT, right. But, the point is, it also add tons of way to use EU to optimize your ressources, to exploits those in a better way: what are Aluminum, electrum, Lava Centrifuging, Silicon Plate, Industrial Grinders and such for you ? Way to get more stuff with energy. That's kind of the point of UUM, except in GT it's quite harder to get everything UUMable with GT machines, but it just makes the game enjoyable much longer.
3) I'm saying that, because I already ended 6 servers because of easy UM + greengens making the point of MC (mining) useless. Of course you can also build and do something else in MC, than mining. But if you really want to do that, then Creative is more appropriate to do so.