I was always a kid trying to make a buck. I borrowed a dollar from my dad went to the penny candy store bought a dollar's worth of candy set up my booth and sold candy for five cents apiece. Ate half my inventory made $2.50 gave my dad back his dollar.
The warrior may fight for gold or for an immediate gain or for something to take home for the winter to feed the family. The soldier is part of a more complex society. He's fighting for a group ethic of some sort.