I'm a marketer :-) Also, I have purchased a non-trivial amount of BI, Analytics, and Marketing software at total contract values as high as $X00K.

I suggest that you offer at least two tiers (personal/education and corporate). You can keep the personal tier low to drive adoption as part of your growth strategy and price your corporate license at $200-$600 per person per year. I have never been in a situation where there was even a need to discuss the cost of a tool at those price points. If it will increase productivity, just buy it.

Lastly, consider an enterprise or site option for users with more than X licenses.