if I may be politically incorrect here, I'd like to say what's at the back of my head.
If client not willing to pay, just do your due diligence and advise on quality. If the shoot's quality is already committed before hand and is already in progress and the budget wasn't factored in, in the first place, then it's the main contractor's fault, and usually the main contractor does have a buffer enough to absorb this.
I do not fault the contractor looking for a cheaper alternative, only that he/she is looking for a cheaper alternative AFTER the contract is awarded in order to maximise another aspect of profit.
If client not willing to pay, just do your due diligence and advise on quality. If the shoot's quality is already committed before hand and is already in progress and the budget wasn't factored in, in the first place, then it's the main contractor's fault, and usually the main contractor does have a buffer enough to absorb this.
I do not fault the contractor looking for a cheaper alternative, only that he/she is looking for a cheaper alternative AFTER the contract is awarded in order to maximise another aspect of profit.