Hallmark Cards Inc. said Monday that it has completed its buyout of Crown Media Holdings. Hallmark of Kansas City, Mo., already owned 90 percent of Crown Media of Studio City. By buying the remaining shares, the privately owned Hallmark can eliminate the costs it paid to keep Crown public, and it can gain some competitive flexibility. Since Crown Media is now private, it canceled its quarterly earnings conference call, scheduled for Tuesday. Hallmark earlier announced it had planned to pay about $175 million to acquire the rest of Crown Media, which owns the cable TV properties Hallmark Channel and Hallmark Movies & Mysteries.