Reference for annual journal subscription costs paid per university?
There is, in fact, a resource with the information you asked for, for institutions in the United States.

Detailed information on individual academic libraries' expenditures (by university) is available from the National Center for Education Statistics in the United States, as part of their Libraries Statistics Program. 

The data from these surveys, including the individual responses from each university, are available for download in plaintext format at this link. The most recent year available is 2012.

To take your example, according to that data, Harvard's expenditures for library resources in 2008 included $9,248,115 for serial subscriptions. In 2012, this number was up to $16,391,638 (the most of any library in the survey).

If you're interested, a set of related information on amounts paid by selected public universities to specific major publishers can be found in 


  Bergstrom, Theodore C., et al. "Evaluating big deal journal bundles." Proceedings of the National Academy of Sciences 111.26 (2014): 9425-9430.


(see especially the supporting information for the latter.)