I'm not referring to Dropbox versus its competitors. I'm suggesting that Dropbox should focus on price discrimination for its own product lineup, because Dropbox apparently (at least as explained by jliptzin) has potential customers with a high variance of willingness to pay.

It seems discrimination is a loaded term. Price Discrimination isn't a bad thing. It refers to the practice of getting a customer to pay exactly what they can for a good. A common example of price discrimination is airline tickets. If you buy a ticket 3 months in advance vs 3 days in advance you essentially pay more for the same product.

What DropBox needs/should/could figure out is a way to sell subscriptions at $10 to those who are comfortable for paying $10 (which seems to me is completely unlikely, when you get competitors, cost tends to go down)