If you want a cut-me-off set to $X, and some lag might allow charges to reach X+Y before the cutoff took effect, which is the customer-centric answer:
a) don't offer ANY cap, simply let the customer's out of control charges just keep racking up to catastrophic levels that put them out of business?
b) cut it off as soon as you DO detect it exceeded their cut-me-off threshold even if by that point it has reached X+Y?
If you want a cut-me-off set to $X, and some lag might allow charges to reach X+Y before the cutoff took effect, which is the customer-centric answer:
a) don't offer ANY cap, simply let the customer's out of control charges just keep racking up to catastrophic levels that put them out of business?
b) cut it off as soon as you DO detect it exceeded their cut-me-off threshold even if by that point it has reached X+Y?