I don't think that there is an artist out there would would not want to produce low volume and make lots of money. If I had my choice why would I want to produce 5,000 "just okay" images and make $2,000 per month if I could produce 500 unique, marketable images and still make $2,000 a month? That is easier said than done. Many people make a living at this and produce a lot of good images because it's their only source of income. Others think they are good artists a produce junk so their sales are low. What do they do in response? Shoot thousands of images just to make that $2,000 a month. It's not about a strategy of "number of images" necessarily, rather are the images you shoot in demand, fill a niche, are good quality and somewhat unique (hard to copy). If you can do this you won't have to shoot thousands of images to make $2,000 a month. If you can produce 5,000 of these good, unique images then you can make a lot more money. Really about balancing your shooting and processing time with the rest of your day, week, month, year, etc.
For example, I have a day job so I don't shoot full time. I put in about 25 hours a week because that's all I can afford with a wife and a life I like to enjoy outside of shooting in my make-shift studio. This means I add about 200-400 images a year that are average, so I don't make much. I don't have any formal education in graphic design or photography, I learn it all on my own. Others in here and not in here have broad backgrounds in this kind of thing and are very good at what they do. Some of the work in stock blows my mind and I am often in awe at what people can do. In the end it comes down to time & experience.