I was responding to the OP's question, which sounded like she was under the impression that "taking a course" is how you get certified. Yes, you have to have the CEU hours to get certified, and continue to accrue CEUs to maintain your certification (and, in many states, your basic licensure).
There are lots of sources for CEUs, and different sources charge different fees for them. The AHEC libraries in my region provide continuing ed offerings, many in psych, at a
much more reasonable cost than a lot of the "for profit" CEU businesses; the local mental health agency or NAMI chapter often have speakers/seminars that offer CEUs, schools of nursing and hospitals often offer speakers/seminars at little or no cost, etc, etc. In my own case, I've always been a member of ISPN (and the ACAPN before it became part of ISPN) and find that attending the national convention each year provides most of the required # of CEUs, plus, I feel that the membership offers me significant
other benefits, as well. (The same is true of APNA, although I'm not an APNA member.)
But I'm not here to recommend any particular source of CEUs -- I was just trying to point out that you don't
have to "buy" CEUs or exam preparation help from the ANCC (or any other particular vendor). It's a big world out there! If you "shop around" a little, you can often meet the continuing ed requirements without spending a lot of $$. Of course, that's assuming that you pursue continuing education on an ongoing, continuous basis, not that you wake up one morning and say, "Wow, I need 30 hours of CEUs by next week!"
And, again, re: the exam itself, the point is
not that you're supposed to have to learn a whole bunch of new stuff for the exam -- it's intended to simply verify that you already know what any competent, experienced psych nurse (in the case of psych certification!

)
already knows. IMHO, all these "certification exam prep courses" are kind of a racket.