$40 per day is weak. Less than California minimum wage. And the risks are considerable. Reminds of the work of Sudhir Venkatesh who found that average wage for drug dealing grunt is about $3.30/hr - not far from what we're seeing here, though at least bot herder doesn't risk being shot. He is right that this thing has no future for him.
Also, why not mine litecoins (cpu's are good at doing that, so no drivers needed and he can mine bitcoins at the same time) and sell them for bitcoins? They are worth enough that his profits would go up noticeably much.
* 30% of victims are Americans.
* 80% have an antivirus installed.
* An average income of $40 per day (bitcoin only). May vary up to $1,000.