Depending on the economic climate and the situation of the company in the marketplace this may be accurate.

If you've got good sales people that are already selling as hard as they can't you won't be able to squeeze much more out of them if the economy tanks and nobody wants your product.

I'm sure there are sales people who have quit due to "the beatings will continue until the morale improves" situations where their quotas keep going up, which cuts their bonuses, effectively acting like a salary cut, in a bad company.