Largesse
Largesse is a battle with consequences all of it's own. My largesse has to beat their largesse, without you giving it to them on a plate.
Military superiority comes from either of a few areas
1] Uniqueness [functional &/or operational superiority] - Outright Superiority, bigger, better.
2] Superiority in numbers - Out number with more forces
3] Allies & distribution - More friends in more places.
Selling it or giving it away only works sometimes. Where [#3] fails you need [#1 or #2], and you have already betrayed yourself [#1] in attempting [#3.]. So that leaves you with [#2] outnumber with redundant forces. The weapons already developed could if required eliminate [#2] so states are left with little wars, spats and quarrels. What make one go all in, when one cannot afford to lose, but cannot win?