If you are going to twist the language to abuse this disadvantage then there won't be a way to stop you from abusing anything written down.The text is clear that "Modifiers: -5 if the offer exceeds twice the cash you currently have on hand."
If you catch Mr. Dwarf at a moment when he's got very little cash on hand, e.g. after having a thief pickpocket his coin purse, not only can you trigger his self control roll but you can make him roll at a -5 penalty, no matter what is required to earn the payoff!
It's very exploitable and it turns Mr. Dwarf into a one-dimensional caricature.
Cash on hand doesn't have to mean in their physical possession. Should count savings, bank accounts.