Since box.com and dropbox are private, that don't disclose that information. However, when they file, they might give some semblance of a breakdown/comparison.
They are, however, pushing hard not just for enterprise customers, but for service contracts and "Box Consulting" services. These are where companies like IBM, etc. really make bank.
So this suggests that individual accounts like those Dropbox is more well-known for, are either unprofitable or very low-margin. This may also explain why Dropbox charges more than everyone else.
They don't split out enterprise revenue but do talk about all their enterprise clients and that it is 59% of the Fortune 500.