(Frederick M. Brown/Getty)

CBS Corp.’s syndication arm is asking $1 million for 30 seconds of national commercial time for the final week of Oprah Winfrey’s TV show in May, ad buyers say.

The stratospheric rate comes close to rivaling events like the Academy Awards, for which ad buyers said they paid between $1.7 million and $1.8 million for a 30-second spot earlier this year.

The rate is being asked without any guarantee of an audience, the buyers say. But they add that many times more viewers than Winfrey’s regular audience of about seven million are expected.

Winfrey’s asking price illustrates the gaping hole she will leave behind in daytime TV as she begins concentrating solely on her cable network, which she owns in a joint venture with Discovery Communications Inc.

Several well-known names are jockeying to grab even a part of her audience. Anderson Cooper will start a new talk show with Time Warner Inc.’s syndication arm this fall. CBS anchor Katie Couric is considering leaving her newscast to start her own talk show for the fall of 2012.

CBS declines to comment specifically on rates for Ms. Winfrey’s final episodes, but it says in a statement: “The final episode of ‘Oprah’ — in fact the final weeks of ‘Oprah’ — will be a TV event,” It compares the show’s end to the finales of “Friends” and “Frasier.”