Kaplan is the complete opposite of 'cost effective' DAT prep. Its bloated, expensive and dated. I took Kaplan live-online and found it to be helpful, but far from the best prep tool, nor the most cost-effective
Ferralis notes for bio (free), Ty Jacobs notes for bio/chem (free) chads videos for gen chem/orgo ($50), DAT bootcamp and DAT genius for all sections ($200 combined), DAT Destroyer ($150), and the ADA 2007 and 2009 practice tests. All in, that's around $400 - not cheap, but not nearly as much as a Kaplan course, and will serve you much better. G'luck