Luxury items are actually a sign of a healthy economy - they mean there's a diversification of the workforce and money being put back into the economy. I'm not sure of exact figures, but I'm fairly certain a large chunk of all religious donations either ends up paying the salary of religious leaders(who then spend that money) or in helping the poor etc, which helps them function in the economy better.
Knowledge is not a golden ideal or an inherent good. After Robert Oppenheimer helped create the atom bomb, he famously remarked that science has known sin. Space exploration, in a similar fashion, had very direct ties to missile technology, which was primarily interesting to the US and USSR for the ability to launch large nuclear warheads thousands of miles in order to kill millions of people from far far away.
As for your comments on war and people, it's hard to reply to such sweeping generalizations. However, suffice to say war is frequently NOT necessary, and the amount of money to be spent on national defense is always up for debate. The consequences of spending too much are historicaly evident, the most recent example being the collapse of the USSR. I hope that no one would agree that we need to spend money to kill, but rather that we need to spend money in order to defend.