Earlier quoted context omitted.
Really? Are you talking gross or net profit? I would be surprised to find many software products where the gross profit margin would be less than 50%.
Dropbox isn't a software product; it's a service. What's more, it's a service that needs to be priced to compete with Apple's own iCloud.
Software and service prices seem mostly arbitrary to me anyway.
How else Aperture went from $300 to $100, Lightroom the same, BBEdit shed 70% of it's price in one day, etc etc... Same, why was iWork a $99 package and now it's 3 components are $10 each on the Mac App Store?