What can reduce building cost multipliers?

[ovni.demon]

What are all the upgrades reducing building cost multipliers?

If you could help me complete the list, I would be thankful:

Goblin bloodline
Goblin upgrade 12 (Non-unique)
Dwarf upgrade 2
Titan upgrade 3 (Hall of Legends)
Fairy upgrades 1, 2, 3 (Farms, Inns, Blacksmiths)
Research Economics 50 (Fairy) (Farms)
Research Economics 135 (Unique)

[Herr Glaube]

I think that's all of them. If you need tons of buildings and faction doesn't matter, Goblinline Dwairy is the way to go.