Group orders of printed materials are frequently organized by professors in my experience, just to get better prices for the students. However, these are usually prefaced with "of course you can acquire these materials on your own, but they're going to be $X if I order them and I believe they are usually $X+z otherwise. Please put your name down on this page if you would like me to order one for you."

It may be that your prof is just bad at communicating. But what's odd in your case is that it seems to a) not be voluntary/your prof didn't give you an alternate avenue to acquire the materials and b) it's just copying worksheets, which should be part of regular expenses. <s>I can't believe the department wouldn't have a copier available for the prof to use for free!</s> Edit: I stand corrected, there are apparently many places where professors are charged for copying, in which case it may be those costs your prof is trying to recoup.