The difference between user interface design and hardware specs is that better usability is derived from one-time expenses for user studies, design iterations, and coding — whereas beefier hardware (say, adding a camera) is a repeated expense for each additional unit manufactured.

This means that even cheap devices can have great usability because the cost of better research and design is amortized across millions of devices. This is why usability has stupendously high ROI for any big project.

— Jakob Nielsen’s Alertbox, “Rebuttal to Critics of Kindle Fire Usability Study”