Beginning this week, theatregoers can go to Cabaret a little more cheaply -- with $25 tickets for weekday evenings and all matinees. Like rush tickets, these rear mezzanine seats are available at the Studio 54 box office the day of show and are subject to availability. There is a limit of 4 tickets per person. The Sam Mendes revival of Kander and Ebb's Cabaret opened on Broadway, March 19, 1998 at the Kit Kat Klub. The Roundabout revival originally starred Alan Cumming as the Emcee, Mary Louise Wilson as Fraulein Schneider and Natasha Richardson as Sally Bowles. Tony Award winner Cumming returned from a hiatus on Dec. 1, joining the present cast of Jennifer Jason Leigh as Sally Bowles, Ron Rifkin as Herr Schultz, Blair Brown as Fraulein Schneider, John Benjamin Hickey as Cliff, Denis O'Hare as Ernst and Michele Pawk as Fraulein Kost. After Leigh and Hickey leave at the end of Feb., Mary McCormack (Howard Stern's "Private Parts" film) and Boyd Gaines (She Loves Me, Company) come in. The show now plays at the larger Studio 54 space. For tickets call (212) 239-6200.