Think about how many lives he ruined.
It's easy to gloss it over because he just took a little piece here and there. Just a few thousand dollars. But he made up for it in volume.
Let's estimate how much he ruined people's lives. The agreement describes 6 million dollars of fraudulent copyright charges. Just as an estimate, assume that the average person makes $20 after taxes (you have to pay the charges with after-tax money)--maybe I'm off by 50% but it'll at least be good as an estimate. That means that 300000 hours of people's lives went to pay for this. Assume that people can work 16 hours a day and you have over 50 years of human beings doing nothing but work 112 hour weeks, eating, and sleeping to pay fraudulent charges.
He's just doing it piecemeal, instead of pushing all the 300000 hours on a single person. But it still adds up. Of course I'm probably off by some factor here (the victims still need to pay for food and housing while working the 50 years, for instance--how do you account for that?) but it seems like 39 years in prison is reasonably close to the damage he caused.