Pro is $8.25 / month for 1TB on annual billing. I rarely see monthly pricing for under 5$. So, I don't think it's going to drop much at this point. https://www.dropbox.com/business/plans-comparison?_tk=dbv1
IMO, 1TB is completly reasonble. You can get ~10 GB of storage several places for free which covers most things and minmaxing 2-3$ per month is generally a waste of time.