@MedicineBall - I can't say that I don't disagree with you, but eye whitening is very important to most people. How often do you see a African American actor with yellow eye whites? The image of beauty happens to include white eyes.
I think that some African American woman like to have their eyes whitened for one simple reason -- their eyes will stand out more against their skin. Contrast always draws attention, so why not improve theirs?
As for the cost, it is not covered by health insurance and it ranges from $2,000USD to $5,000USD per eye. It is definitely expensive, but if you have severely red eyes – it might be worth it.