4,000,000?!!!
Speculating, but it would be more realistic if you could "donate" any amount to help and that those donations tallied up to meet the requirements. If the amount isn't met then the defence force takes significant hits, so there is more focus on multiple donations rather than big hits. Big hit donations like this should generate huge future rewards/rep.
having had a fair amount of experience of fundraising (was my wife's line of work), it's about the smaller repeat donations rather than the one offs. So in this case it would be great if the game could track donations yours vs total and pay out rep with that faction accordingly. Not that i am being greedy or anything, lol.