Roof lanterns are a pretty great roof light product which differ from a more typical roof light in a number of important attributes, including the all important price. This cheaper price range is basically down to how it consists a number of pieces of glass, while a roof light filling a similar space as a roof lanterns would be more expensive because of its size and the difficulty with producing something of that size.
Other attributes of roof lights also make them ideal for a number of different situations. For instance, you can include an automatic vent opening system with one of the smaller windows, which would be far more difficult to do with a large roof light.
Another thing worth considering is the affects on the interior design of your home. Due to the domed style of a roof lantern you can get a completely different experience from them, which can give people the feeling of extra space and openness.