TinSoldier
This is part of the same bug which stopped players from participating in war or receiving/donating troops while asking them to update the game. This bug appeared after the servers were down for 1h-2h few days back.
You need to uninstall and re-install Dominations for new updated cost to take effect.
Make sure that your Dominations ID is connected to Google Play(for Android) or Game Center(Apple iOS) so you don't lose your progress.