Gao Guang could now ruthlessly fleece Lord a big one because he said any amount of money would do.
Being a mercenary is an unruly profession, but there are also some rules that must be followed. If an arms dealer delivers life-saving goods in desperate times and they're used without a pre-agreed price, the price is at the seller's discretion.
Take the Cloud Burst Bomb for instance, Gao Guang could quote a million, ten million, or even thirty million to make Knight's effort utterly in vain, forcing them to further compensate for travel expenses and pensions.
If the figure demanded exceeds the commission, that's an arms dealer being unreasonable. Making mercenaries work for nothing and lose money is changing aid to profiteering during a crisis. If the deal looks that ugly and faces are turned, one can't blame anyone else.