$32M is not a cost the requestor bears, but an estimate of the cost the city bears.
IT estimated the requestor fees to be $21k/year assuming 10TB of data.
Clearly, IT were estimating the costs of releasing all email text, because FOIA mistakenly changed the words "please provide the following information:" to "including metadata:"
Once they figured out the request was for header information only, the city came back with an estimate of under $60.