I would gladly pay $20 for a Fall From Heaven DLC. I'd Pre-Order that. Donate money, start a petition, ask my congressman and shoot an Alaskan to get FFH on Civ 5.
Maps: Maps are free.
Leaders: they are free too.
Full Civilization Adds: Maybe. Im disapointed I cant play as the Mongols on Multiplayer... nor the Babylonians. Why pay more for solo content? It'd really have to be something special like Celts: Guerrila Warrior Unit, Special Building Grazing Area: +15% food in city, +1 production from horse pastures. Civic Trait: While at war you gain +25% production in all cities that have a military unit garrisoned in them. It'd have to have the awesome Narration and flavor of all the other civilizations. Even then it is still a maybe.
Mods: I'd pay a buck or two for them if they looked polished. A good American Revolution mod or WW1, WW2, 100 years war... anything. As long as its playable from multiple angles and polished and unique.
Please let there be a Fall From Heaven!!!