Nashville, Tenn. - The grass-roots movement that exploded across the nation last year in revolt against President Obama's economic policies and health care agenda reached a critical milestone Thursday as hundreds of conservative activists converged here for the start of the inaugural National Tea Party Convention.

But the first gathering of a sprawling movement, made up of hundreds of disparate Tea Party groups, has been marred by controversy. Some high-profile speakers and activist groups have canceled their appearances in protest of alleged profiteering by the convention organizers.

Attendees have been charged $549 a ticket (plus hotel and transportation) to gather for three days at the luxurious Gaylord Opryland Hotel and Convention Center - an expense that critics say is out of reach for the average grass-roots activist. Some of the proceeds will go to cover former Alaska governor Sarah Palin's reported $100,000 fee to deliver Saturday's keynote address.

Despite the fractiousness, however, officials said the convention is sold out, with 600 "delegates" coming. The closing banquet, featuring Palin, has sold 1,100 tickets, and organizers say they can accommodate more, at $349 per seat.

Unlike the mass protests and town-hall rage that has come to define the movement in its first year, the convention is designed to demonstrate that the Tea Party movement is "growing up," said convention spokesman Mark Skoda, chairman of the Memphis Tea Party. There are sessions on leadership, political philosophy and such nuts-and-bolts political topics as "how to do voter registration drives," as movement leaders try to turn grass-roots power into political gain in November's midterm elections and beyond.

"We are all very mature people - without the pointy hats and the signs," Skoda said. "You will see people of quality and maturity to help bring this movement to a pinnacle whereby we actually change politics."

Hundreds of independent Tea Party groups have sprouted over the past 12 months, in small towns and major cities alike. Their members have divergent political views, and their leaders have publicly quarreled over tactics. But the groups have largely united around a common cause: a don't-tread-on-me brand of fiscal conservatism and a belief that the federal government, first under President George W. Bush and now under Obama, has recklessly plunged the nation further into debt and overstepped its constitutional powers.

"If you take 1,000 so-called Tea Partiers and ask them what this movement is, you'll get 1,000 different interpretations," said Mark Williams, a talk-radio host and chairman of the Tea Party Express, which will begin a nationwide bus tour next month featuring Palin. "I've had pro-lifers practically standing next to pro-choicers, and gun-control people standing next to people with a pistol strapped to their hips. But they're all waving American flags and speaking out against the galloping socialist agenda."

The convention promises to draw intense worldwide media attention. Skoda said he has credentialed hundreds of reporters and producers to cover the convention, including from across Europe and Asia. Japan's NHK network plans to broadcast the convention in high-definition television, Skoda said, while Fox News and MSNBC have announced they would air Palin's speech live in the United States.

Palin plans to speak for about 45 minutes Saturday night, followed by a 15-minute question-and-answer session with audience members who pre-submitted questions. Despite her appearance fee, Palin said this week she would not "benefit financially" from the event. "Any compensation for my appearance will go right back to the cause," she wrote in an opinion article published in USA Today.

Palin did not specify how she would redistribute her earnings, and Skoda said he did not know.

In her article, Palin drew historical comparisons between the Tea Party movement and the march for American independence, as well as connecting it to the civil rights movement of the 1960s.

"The spark of patriotic indignation that inspired those who fought for our independence and those who marched peacefully for civil rights has ignited once again," Palin wrote. She added: "From the town halls last summer to the protests and marches in the fall to the game-changing recent elections, it has been inspiring to see real people - not politicos or inside-the-beltway professionals - speak out for common-sense conservative policies and values."

Tea Party Nation, a group that started as a social networking site linking conservative grass-roots activists, is organizing the convention. The group faced criticism from leaders of other Tea Party groups for the convention's price tag. Tea Party Nation founders Judson and Sherry Phillips recently acknowledged their group is a for-profit corporation, but said any profit from the event will be funneled back into the Tea Party cause.

"We have made the best of a tight budget and scaled back the price of attending this convention as much as we could without putting TPN into bankruptcy," Sherry Phillips wrote recently in an e-mail to members.

Still, other prominent voices in the movement remain furious about the financial setup. Erick Erickson, editor of RedState.com, a conservative blog, wrote that the convention "smells scammy." Two Tea Party groups, the American Liberty Alliance and the National Precinct Alliance, withdrew from the convention in protest, as did two featured speakers, Rep. Michele Bachmann, R-Minn., and Rep. Marsha Blackburn, R-Tenn.

"The average Tea Party person is going to be sitting on their couch at home because they can't afford $600 for a lobster-and-steak dinner in a fancy hotel," said Anthony Shreeve, 27, a Tea Party organizer from Tennessee who is boycotting the convention and Palin's speech. "It didn't sound "Tea Party' to me. It sounded more like a regular Republican fundraiser."

Philip Glass, director of the National Precinct Alliance, said that he believes the convention "won't change anything." He said time and resources would be better (spent working through the Republican Party system, from the bottom up, by helping grass-roots conservatives take over local precincts, parties and, ultimately, elected offices.

"It's nothing more than a feel-good gathering of like-minded individuals doing nothing that's tangible or effective," Glass said. "Once those people leave there, what is it that they're going to do? Are they going to do something tangible? Or are they going to go home and just sit on the couch?"