My neighbour came to me last week to ask for help. Exactly that had happened to him, from of all things a Facebook ad. It was a simple matter of killing the browser, but it had put up a phone number for "support" that he had already called, but which was busy... so I guess they were having a fair amount of success. Wish I'd taken a photo.
"Hi there! Your computer has been infected with a virus which will encrypt one file on your computer at random each day. You can stop this, and decrypt all the files by paying X to bitcoin wallet Y. Don't wait too long, because if you wait too long, we might encrypt some system file and it won't boot any more."
and which did nothing else whatsoever
...then you'd probably actually get some income.
It'd be an interesting (if ethically awful) sociological experiment to find out exactly how much. Returning people's money afterwards, of course.