Dropbox and shared folders

We know that Dropbox uses Amazon S3 for its storage back-ends. For 2GB of storage, Amazon will charge them $.30 (assuming $.15/GB). This obviously doesn't include their other hosting costs but we're using it as a basic measurement.

Once you start using shared folders (especially if your company starts creating shared folders), then pretty quickly your storage capacity gets filled up. You have to look at Dropbox's simple statement here:
https://www.dropbox.com/help/14

When you sign up for a free Dropbox account, we'll give you 2GB of storage space forever. Deleted files and previous versions of files don't count against your quota, but any shared folders you have joined do.

The implications are huge about using shared folders. This statement pretty much means that every person who ends up using the shared folder has to be upgraded to a $10/month plan, which means that Dropbox can comfortably begin to make more than 10x for each user account once they're dependent on using it. And the organization that uses the share folders also must pay for the monthly cost to increase storage quota as well!