There can be advantages for coalitions in a war. There are also disadvantages. However, this is not the point I made. The only point I made is that $x spent

There can be advantages for coalitions in a war. There are also disadvantages. However, this is not the point I made. The only point I made is that $x spent by say 15 countries on defense is not at all equivalent to $x spent by a single country on defense in terms of military power, force projection, etc. due to the aforementioned duplication of HR, admin and other ancillary roles in supporting a military force.