Museums in most cases do not own the copyright to the works in their collections, yet they often pretend they do to be able to charge higher processing fees.

http://copyright.columbia.edu/copyright/2011/06/27/copyright...

Of course they can ask money for the cost of for example photographing, scanning etc., it is just not correct to say it is for copyright licensing.

I thought it was obvious that I did not mean copyright of the exhibits but of reproductions like scans. Thanks for your clarifications.

Scans don't meet the threshold requirement of originality under US copyright law. See for example Batlin v. Snyder - https://scholar.google.com/scholar_case?q=originality+museum...

Yes, museums like to claims this to make money. This does not make them right.