There was nothing mentioned regarding passport pages in the press releases, so I went to Regulations.gov to read the proposed rule. According to the rule, there
would be a fee imposed in order have visa pages added:
In the past, the Department provided extra pages in a customer's
passport, to which foreign countries' visas may then be affixed, at no
charge. The CoSS found that the cost of the pages themselves, of having
the pages placed in the book in a secure manner by trained personnel,
and of completing the required security checks results in a cost to the
U.S. Government of $82.48 based on a projected FY10 workload of
218,000. Therefore, the Department will charge $82 for this service.
Here is the full text of the proposed rule. You can comment on the proposed rule until March 11. These fee increases have not been put into place yet, although it's likely that they will be.
The OP is correct about the visa fee increasing to $150 for some visas, but
not tourist, business or student/exchange visas. The proposed increase for those visas is $140 USD. (Point being: The fee at Ezeiza will likely increase from $131 to $140 USD.)
I find it rather unbelievable that it costs the Department of State more than $17,000,000 per year to add pages to a passport. What kind of work could they possibly have to do in an hour (or 20 minutes, as one poster has said) that warrants a cost of $82 USD?