Talk was never cheap for Rush Limbaugh, but now it is getting a lot more expensive.

The AM radio host will be paid about $400 million to continue serving up his daily dose of conservative talk through 2016. His $50-million-a-year paycheck represents a raise of about $14.4 million a year over his current contract, which was paying him $285 million over eight years and was set to expire in 2009.

The deal is thought to be the most expensive in radio since Howard Stern moved to Sirius Satellite Radio for a reported $500 million in 2004.

“I’m not retiring until every American agrees with me,” Limbaugh, 57, said on his radio program Wednesday.

The deal amounts to a major bet by Clear Channel Communications and its syndication subsidiary, Premiere Radio Networks, that Limbaugh’s brand of conservative talk will prosper well into the next decade. The company announced the contract renewal on Wednesday, though the financial details were supplied by Limbaugh in an interview with The New York Times Magazine for an article that was posted online at www .nytimes.com on Wednesday and will appear in print on Sunday.

Limbaugh’s windfall comes at an acutely tough time for the radio industry, which has been troubled by technologies like iPods and a sluggish advertising climate. The total time spent listening to radio has fallen 16 percent in the last decade, according to data compiled by Arbitron, the measurement firm.

Advertisers have taken note: Nielsen Monitor-Plus, an advertising information service, measured a 3.6 percent decline in national radio spending last year.

“Frankly, since 2001, we’ve had a number of things going against us,” said Jeff Haley, the chief executive of the Radio Advertising Bureau.

In April, the bureau, a trade group, helped introduce “Radio Heard Here,” a marketing campaign that is meant to reiterate the medium’s relevance and emphasize that it reaches 235 million listeners a week. “Rush represents the reach of radio,” Haley said.

Certainly, the eight-year contract and large payout for Limbaugh underscore his position as the leading purveyor of political talk radio. Only a handful of other radio personalities — like Stern, Paul Harvey, Ryan Seacrest, Sean Hannity and Glenn Beck — have anywhere near the same recognition and power to name their prices.

“Limbaugh is a master of the airwaves,” said Michael Harrison, the editor of the radio industry publication Talkers Magazine, in a telephone interview Wednesday. “He is the best talent on the air in modern broadcasting.”

Limbaugh’s existing contract, which was worth $285 million over eight years, was set to expire next year. His show — which is on every weekday from noon to 3 p.m. Eastern time — attracts 3.5 million listeners in an average quarter-hour, and reaches an unparalleled audience of nearly 20 million in an average week, according to Premiere. This makes him the country’s most popular news-talk host by far.

“Broadcasters of Rush’s quality come along once in a lifetime,” John Hogan, the chief executive of Clear Channel Radio, said in a statement on Wednesday. “We’re privileged to continue our relationship which is unprecedented in the history of our industry.”

Limbaugh’s success is especially significant given the difficulties of the radio business, which is challenged not only by portable music devices but also by satellite services like Sirius and the growing availability of other entertainment options.

“The terrestrial radio industry must provide the best possible programming or it will not survive in the face of the competition on the Internet and from other new technologies,” said Harrison of Talkers Magazine.

He added, “The industry has to make sure it has the major league stars in broadcasting; therefore, it makes sense that the most money and the longest contract would go to the biggest star in radio today, and that’s Rush.”