says that CRS (Congressional Research Service) estimated World War 2 was to be around $4.1 trillion dollars!(https://en.wikipedia.org/wiki/Financial_cost_of_the_Iraq_War) That's more than the Saudi Royal Family´s worth (https://www.cheatsheet.com/culture/royal-family-worth-over-1-trillion.html/) and British Royal Family's worth (https://www.businessinsider.com/british-royal-family-richest-people-2017-11) joined together. We could use this money for a ore important cause like donations to charity, or donations to organizations. So, if we stop wars we can donate a lot of money to good causes and not bad causes like war. Also, According to Wikipedia's article: 

 a Congressional Budget Office (CBO) report published in October 2007, the US wars in Iraq and Afghanistan could cost taxpayers a total of $2.4 trillion by 2017, including interest. Maybe without war, there will be less homeless people, because of a lot of donations to charity.

Another reason why wars should be stopped is; countries will be destroyed. The Soviet Union lost 27,000,000 military and civilians. (https://en.wikipedia.org/wiki/World_War_II_casualties_of_the_Soviet_Union) This is almost thrice the population of UAE(which is 9.89 million, according to        http://worldpopulationreview.com/countries/united-arab-emirates-population/). Another example is after the Anglo-French War (1778–1783), Britain had many debts, and had almost no cash left in banks and was desperate. So, they taxed American colonists. If another country is in the same situation and taxes the civilians, it could lead to protests, which might lead to some deaths. This could start another war. After World War 2, Japan owed the Allies $1.02 billion worth of goods and services to Philippines, Indonesia, Burma, and (later) South Vietnam ( according to the Washington Post, which is a famous newspaper company).