How many people need 2TB or even 1TB / 500GB of St orange on Dropbox? Mostly companies and persons that use it for profit.
For me 100 GB or even 50 GB and no device limit (!) is enough. Give me that for $12 a year and I won't look for alternatives.
How many people would use that? I think more than the $10/month plan.
How many people who currently pay $10/month would drop down to a $3/month plan if given the option?
I'm fairly certain the math on this paints a clear picture: Offering a $3/month plan would cost them more than it makes them.