Me too. I'm trying to find better ARPU metrics to ensure I'm not misunderstanding that vague "over 17%" statement. As a company they tend to report "Number of Paying Customers" which are businesses and only occasionally reference individual user accounts.

Though simply looking at per user per month pricing:

    Dropbox for Business has $15, $25, and Enterprise
    Dropbox Individual has Free, $10, and $20
    Box.com has $5, $15, $25, and Enterprise

The math doesn't even really make sense though. Dropbox's ARPU is $8/user/mo whereas Box is $4/user/mo. Either the my math is wrong or Box offers some pretty steep Enterprise discounts that work out to <$5/user/mo.