Wars have never been cheap

the crusades made a lot of money to the church

The Anglo-Zanzibar War fought between the United Kingdom and the Zanzibar Sultanate on 27 August 1896 lasted around 40 minutes and resulted in 500 Zanzibar casualties and 1 injured British sailor (who probably slopped some hot water on his hand while making the tea). That must have been a pretty cost effective war.