Merger partners Caremark ( CMX) and CVS ( CVS) are full of cutting comments lately. This week, Caremark, a Nashville, Tenn., mail-order pharmacy, rejected an unsolicited buyout bid from rival Express Scripts ( ESRX). Caremark prefers to join with big drugstore chain CVS. Caremark scoffs that the Express Script deal "lacks strategic rationale" and presents regulatory hurdles, while CVS scorns a threatened Express Scripts proxy fight as "nothing more than a publicity stunt." Caremark defends its choice of CVS as a partner, claiming "thorough consideration and consultation with its legal and financial advisers." As financial advice goes, though, Caremark's was on the unorthodox side . On the basis of recent prices, the cash-and-stock Express Scripts deal carries a 9% premium to the all-stock CVS proposal. But does Caremark care? No. It insists other numbers are more germane. "Caremark has substantial doubts," its press release revealed late Sunday, "regarding the reliability of the synergy estimates espoused by Express Scripts." Synergies represent the savings that acquiring companies expect to realize in a deal, typically through job cuts. The figures are notoriously squishy and are calculated mainly to impress bloodthirsty Wall Street types. In this case, CVS and Express Scripts each pledge to wring around $500 million in gains out of a Caremark buy. But apparently all savings aren't created equal. While applauding its own "extensive due diligence and integration planning," CVS snipes that Express Scripts' estimates are "unsubstantiated." Caremark cautions that Express Scripts fails to account for a possible loss of business -- or for the "potential for additional negative synergies." CVS and Caremark are already realizing those in spades. Dumb-o-Meter score: 93. Conveniently, CVS raised its gold-plated synergy estimate by $100 million after Express Scripts declared its own target.