I strongly disagree with that. Its overpriced to be sure, but not a waste. I did kaplan and went from straight 19's on my first application cycle to 22AA, 22TS, 24 PAT on my second. For me, it was worth every penny- in the long run its a drop in the bucket and its the single best thing you can do to improve you application. Also, if you don't improve they'll give you back your money.
I think overall the online materials are the best deal though, they were alot more important for my success than the class. The best preparation for the DAT is taking as many computer-based practice tests as possible.