So Box suffered the pain of being the first in the easy consumer/business online storage category to IPO -- but Box's numbers are now driving valuation of their competitor.
Dropbox: $1B in revenue / $10B valuation (10x)
Box: $400M in revenue / $3B valuation (7.5x)
The real question is earnings(which we don't know yet for Box) and whether Dropbox has a compelling case that it grow faster than Box to justify the higher multiple.
The real issue for me is that file storage is ultimately low profit margin business when the growth maxes out. The end game comes in next 5 - 10 years during a downturn and Amazon, Google, Microsoft, Facebook, or some Chinese company buys one or both of them out and gets the brand and the customers.
Your Box multiples look to be correct - looks like they trade at 6.1x on a trailing twelve month revenue basis, and ~5.0x on a next twelve months revenue basis.
Given that Dropbox has a $10BN valuation and a $600MM line of credit from the big banks, I would expect that their trailing revenue multiple is ~10.0x.