Ever heard the phrase 'Breach of contract'? MUCH more expensive than fulfilling the obligations.
Ever heard the phrase "Haha try and stop me!" ? Look at all of the treaties American settlers made with Indians. Look how many of those we kept. If there's nobody there to stop you, all the contracts in the world are meaningless.
Mercenaries aren't stupid. As a merc, which job would you pick? The one that lets you work out all day, or the one where you get to fight the guy who got to work out all day?
You're gonna have to clarify what you mean by this because I have no idea what you're getting at here.