Any ideas on who (consultancy?) might be able look at the scope/spend and provide reliable benchmarking data? I'm looking to find cost/price benchmarking for my large organization's print spend.

Is this managed print services (copies and printed pages)?  If so, any of the several players out there will do an analysis (if requested) as part of an RFP.  Alternately, some of the small groups (I'm thinking of Technology Integration Group, tig.com) may do a review of data for a few thousand dollars.  I had TIG do a white paper with a similar motive about four years ago.

Consultancies like Deloitte, Accenture, or specialized firms such as Keypoint Intelligence can assist in assessing your large organization's print spend and provide reliable benchmarking data for cost and pricing analysis.

Typically consulting firms like big 4s, research and advisory firms creates this annually and can be used for customized study we well.