My sister is severely disabled (mentally and physically) and goes to a day program for people like her. At the program there are basically two different groups, those who can do some types of jobs, and those who basically can't do anything. They are split into smaller groups, but that's generally how it's laid out. All of these people have mental disabilities though so it's not like blind or deaf people are being taken advantage of here.
My sister falls into the group that really can't do anything so I'm only partially familiar with the people who can do some types of jobs. If they work at the "workshop", they do get way less than minimum wage but it's also very repetitive and low skill type jobs. The local casinos are actually a big supporter of the program because one of jobs at the workshop is to rebuild decks of cards so that they can be sold at the casino as a souvenir. Most of the things they do are like this and involve sorting, packaging, etc. These are still very disabled people but they can do repetitive stuff. If they are "higher functioning", they go out into the community in groups and do jobs at places like Wal-Mart with their helper. I'm not sure how much these people get paid, but it's probably much closer to minimum wage.
In general though, these jobs are more for the benefit of the disabled person so they feel like they are doing something productive. It's not a significant source of income but since the day program facility gets some money for the work, they have to pass something on to the workers. They probably would be watching TV or doing coloring books otherwise, which they more or less do when they are done with the day program and go back to their group homes.
Anyway, I know it doesn't make sense that people with disabilities could be paid 20 cents/hour, but these programs are quite good as it's really designed for people with severe disabilities. It's not for people who have higher functioning autism, just in a wheelchair, bad back, deaf, etc. If they are working at a job similar to what a nondisabled person does, they will get a similar pay.