Skeptics are clicking their tongues this morning over Barbra Streisand's announcement yesterday that come September she will have sung farewell to concert performing forever. The star, 58, has made the announcement before, as recently as the beginning of this year, at the time of her Las Vegas MGM Grand New Year's Eve concert. Still, on Wednesday her manager Martin Erlichman issued a statement saying, "Ms. Streisand has chosen to conclude her public performance career in the two cities most closely associated with her work." The four new final concerts are scheduled to take place Sept. 20-21 at Los Angeles's Staples Center and Sept. 27-28 at New York's Madison Square Garden. (Variety reports that on Aug. 17 she will also sing three songs at L.A.'s Shrine Auditorium, following Al Gore's nomination at the Democratic National Convention.) Tickets for the Staples and Garden performances may go for as much as $2,500 each, say reports.