If this is valuable, they think 10GB is enough to test the fundamental premise and see people hit the edges of what they'd want to pay for.
There might be a segment of the market for whom this is worth vastly more than $5 / month. There might be a segment who wants to pay that little, but it's not about storage. They may not learn these things by priming people on a per-GB storage model.
It's not reliable for storing customer data, no. But it's quite useful for a lot of quick engineering work.
I also failed to mention that having an internal namespace for an organization may be relevant. People may not want to be public.
And, are you suggesting that a corporate process has to rely on technology that is always available? I'm fairly sure that they don't. If corporate Wi-Fi and Microsoft Office are any indication, anyways.
Please excuse any punctuation or capitalization today. I am training a new interface to Hacker News and the voice recognition sometimes produces slightly odd text.