I've sold in the past a lots of dupes, just lately I'm collecting them looking forward for sacrifice.
Current inventory has now (without the original/first ones):
4 x Mummies
3 x Storms
2 x SoL
1 x RttH
4 x Warrior Golden Son
4 x Warrior Soulless Demon
2 x Blue Allied Soldier
2 x Blue Axis Soldiers
2 x Angel of Pain
2 x Gunner Dogs
2 x Green Pyros
2 x Green Alied Bomber
1 x Red Pyro
Not so much, but I think that if we could keep all the Oxes, Harpies and Meatheads we've got through the Book, everyone would have now an army of those.. :D