To be fair, there are also various counterarguments that a rational being should take into account before going to war:

- The likelihood of being killed (IMO big these days, even as a non-combatant)

- the likelihood of suffering from indirect negative consequences via redirection of economic output (IMO high)

- the likelihood of warriors benefiting from the seized resources in a significant way (IMO small, unless you're also part of the ruling class)

So, yes, I agree with your conclusion but there are additional premises at work.