Something doesn't make sense: How can it be worthwhile for the attackers to invest that much time in gaining access to one computer? Given wrong numbers and that many people won't answer the phone, be near the computer, have time at that moment, or be willing to cooperate, and then add the time it takes to talk an end user through such a process, will they gain access to even one computer every 2 hours? How can that…
My assumption is that the scammers are based in India or somewhere else where dollars go quite a bit farther than the US. Even apart from the potential for fraudulent charges, spending a few days to earn a few hundred dollars is definitely worth it in a country where the average income for a year is around $1300.