I just wrote some code to edit costs of Civis and Technologies(had a hard time with it, cuz Civ seems to care about attributes order in XML files, but managed to overcome it). I could make a simple gui if you'd like to check it out. The only thing I've found regarding costs edits are just few edited xmls, so I thought somebody could find it useful. The code makes change to Base\Assets\Gameplay\Data\Civics.xml and Technologies.xml. Edit1: It's also possible to change the boosts.