A Combination Padlock
Shutterstock = $1.50/month
IStockPhoto = $4.00/month
Fotolia = $0.10/month
Dreamstime = $0.10/month
GraphicRiver = $0.50/month
Green Environment Icons Set
Shutterstock = $8.00/month
IStockPhoto = $5.00/month
Fotolia = $0.50/month
Dreamstime = $0.20/month
GraphicRiver = $5.00/month
Looking at the two example above, you can see that a good vector can make about 10x times more than an average one.
Shutterstock, IStockPhoto, and GraphicRiver can make some worthy earnings, whereas Fotolia and Dreamstime are almost hopeless. However, this does not mean you should forget about Fotolia and Dreamstime because the above are only two small examples. Sometimes, Fotolia and Dreamstime can make even more profit from a single item, but the chances are low.
As for photos (not vector), I could not give you a good example as I do not upload photos. But earnings from photos are normally 10x times lower than a vector, unless you have a very good photo which can sometimes make $5/day.
