They should have been able to dedicate half the money for the same revenue, or the same money for double the rev, in your scenario.
Put another way, the estimate is that they pay out $500 for $2k in revenue, then someone came in and dumped a bunch of bots in the way and ate away half their revenue. It's not like those empty clicks are people who just weren't compelled to buy what they were selling. They are bots intentionally disrupting commerce.