Steve Keene is an artist who produces a ton of paintings. He currently claims over 140,000 paintings sold, and has been working since the mid-90's. He paints roughly fifty paintings at once (generally on plywood), using an assembly-line technique, and sells them cheap. On his website you can buy his stuff super-cheap. Currently listed: "5 PAINTINGS THAT KIND OF RANGE FROM LARGE TO MEDIUM" for $21 + shipping. He selects items from whatever he's working on at the moment and just sends it to you. Five paintings for $21? That's a pretty good deal.
If you do the math and estimate $4.20 per painting based on the figure above, Keene has brought in over half a million bucks with his paintings. Granted, that's been over a 15+ year career, so it works out to a typical middle-class income (though that's before the expenses for plywood, paint, space to work, and so on).
Keene's website explains why he produces so many paintings, and why he prices them like he does:
Steve says, "I want buying my paintings to be like buying a CD: it's cheap, it's art and it changes your life, but the object has no status. Musicians create something for the moment, something with no boundaries and that kind of expansiveness is what I want to come across in my work." In the past few years, he has collaborated with the Silver Jews, Pavement, The Apples in Stereo, Soul Coughing, Dave Matthews Band and Merzbow to create album art, video sets, stage sets and posters. Currently Steve [has] sold more than 140,000 paintings.
Here's a remarkably good 12-minute documentary about Keene, showing his process in 1998. It's called "Over 36,000 Sold" -- I guess another 104,000+ have been sold since 1998. It was done by (then) Tisch student Brett Vapnek, who has gone on to direct music videos for the likes of Spoon, Cat Power, and Sleater Kinney.
For more on the world of Steve Keene, check out the SKSK blog, which includes recent videos showing lots of his recent work.