Individual users of Dropbox cannot purchase more space beyond 1Tb. Dropbox is refusing to service these customers and instead tries to get them on a business plan. The business plan is x 4.5 more expensive requiring a minimum of 3 users. Worse still, DropBox spams individual users to upgrade to a business plan with popups using the DropBox application installed on their machine.
https://www.dropbox.com/plans