Additionally, it supposes that all images being solved are the kind that a human must do. Tons of CAPTCHA images being output by naive generators can be solved automatically. I'd be surprised if every image submitted isn't going through an automated solver first with only the < 95% confidence ones being sent to a human.
Actually, you could do a hybrid model where every image is auto-solved and a human can either click to confirm that the auto-solver got it right or manually type a new response. That should get your time per solve down to a second or two each.
Yes, that's how I'd do it too, but I don't know if they're that sophisticated yet (they'll get there though).
Even with 1 second per solve, that's only $3.60 per hour. A massive improvement over 13c, but still certainly not worth anyone in my country's time.
"Spammers Pay Others to Answer Security Tests"[1]
choice quotes:
"spammers are paying people in India, Bangladesh, China and other developing countries to tackle ... captchas"
"attractive enough to lure young people in developing countries where even 50 cents an hour is considered a decent wage. Unskilled male farm workers earn about $2 a day in many parts of India. "
"students typically work two and a half to three hours a day from their homes and make at least $6 every 15 days"
"Another operator in Bangladesh who goes by the screen name Workcaptcha on Freelancer.com boasts on his profile page that his firm has 30 computers, up from just five a year ago. Three shifts of workers allow the operation to hum 24 hours a day, seven days a week"
[1] http://www.nytimes.com/2010/04/26/technology/26captcha.html?...
"This company help many poor company. I am received big position for gaf help so pls maintain gaf term & condition. I am really Love gaf & must going lifetime relation. Gaf best in this world. Trusty, Reliable & more. Thanks" - workcaptcha, Bhai Bhai Data Entry Service
????
> So they build all these CAPTCHA "breaking" sites that actually just return the correct result from their internal databases
Oh, haha, I see ;)
This system has to be using enforced labour, no-one will work for that little, even in the poorest countries. And that 13 cents figure is assuming that 100% of revenue goes to the individual worker.
Taking the best case from the reported average of 10-15 seconds, that means an operator can solve 360 captchas per hour; an hourly revenue per worker of 36 cents.
I have a suspicion that this makes use of a similar 'economy' as the one about Chinese prisoners being forced to farm gold in WoW[1]
If you have just ten 'workers' on 12 hour shifts, that's $43 per day, $301 per week, $15,652 per year. The numbers start to stack up fairly well in bulk - assuming all 1.5 million Chinese prisoners[2] were able to sustain 12 hour shifts 365 days a year and maintain an average of 10 seconds per solve (and that there was a constant supply of paying customers), that's over 2 billion dollars annual revenue. Obviously that number's way off, but probably not by an order magnitude.
[1] http://www.pcworld.com/article/228716/chinese_prisoners_alle...
[2] As of 2006: http://www.kcl.ac.uk/depsta/law/research/icps/downloads/worl... [PDF]