No, to get the discounted tier pricing it must be a single, institution-wide subscription. The benefits of an environment like Box are viral collaborations and connections that occur between individuals and groups by allowing the entire community to quickly and easily share files.
Offering Box to a single department at full commercial prices would generally cost more than deploying Box at the tier based price to an entire campus. This program is also intended to provide very favorable cost terms and minimise the contracting effort for the members.
If your organisation is interested in purchasing Box on a smaller level, you will not be eligible to receive the tier pricing.