In any case, I doubt Stanley can win a bidding war against the Coalition. (Stanley just has a 150K treasury, plus or minus his net cashflow for the past couple turns; the Coalition presumably has the resources of a number of member cities and treasuries.)
Also, it's likely that standard merc contracts can't simply be bought out by the other side once agreed to -- that would make it too risky to hire mercenaries, which would be bad for the business.