From Pixels To Paper

Cost Rises With Image Size

As you can see, the cost rises dramatically as you exceed the 7x9˝ range. Because the required area of a CCD (Charge Coupled Device: a chip that measures the light hitting each pixel) array needed to capture larger and larger images grows exponentially, the cost seems to grow at least logarithmically. So even as the lower resolution range cameras become very cheap, the higher resolution range will stay relatively expensive.