A stand of the BitClave search engine at Blockchain Life 2017, a conference on bitcoin, blockchain, and cryptocurrency, in St. Petersburg, Russia, September 26, 2017. Alexander Demianchuk | TASS | Getty Images

After bitcoin's explosive surge in the latter part of 2017, the crowd at the flagship annual cryptocurrency conference has grown three times as large. An estimated 8,500 are attending CoinDesk's Consensus 2018 this week in New York City, according to Barry Silbert, CEO and founder of parent company Digital Currency Group. Tweet That's more than triple the 2,700 attendees CoinDesk reported for the May 2017 conference. At roughly $2,000 a ticket, that means the conference is raking in at least $17 million in ticket sales alone this year. Last-minute admission is $3,000 a head.

CoinDesk declined to comment on revenue.

"I've never seen anything like this for registration," said Consensus attendee Jeff Denton, senior director of global secure supply chain at AmerisourceBergen in Philadelphia. "I've been on line for an hour." "It's expensive, but it's the largest one in the U.S., so hopefully that brings the value for the cost," Denton said. He said his company is very interested in blockchain and how it can be applied to health care. When the three-day conference kicked off Monday morning, the crowd at the New York Hilton Midtown was so large that it took one CNBC reporter over 75 minutes to get her entrance badge. The line went across the Hilton lobby and continued on another floor connected by an escalator.

Many attendees had to wait more than an hour to register at CoinDesk’s Consensus 2018 conference at the New York Hilton Midtown. Kate Rooney | CNBC

"Whilst we apologize for any delays, Consensus 2018 has received overwhelming interest and is the largest blockchain-focused event ever held in the United States," Jacob Donnelly, director of marketing at CoinDesk, said in a statement. "We are working to reduce the wait time." During last year's conference, bitcoin accelerated its gains above $2,000. The cryptocurrency went on to top $19,000 seven months later in December. But it has since lost more than half its value and was trading near $8,700 Monday morning. More than 20 other events, some with similarly high entrance fees, are scheduled around Consensus as part of a "Blockchain Week NYC," an event run in partnership with the New York Economic Development Corporation. "It is a bit chaotic in here," said Ronnie Moas, head of independent market research firm Standpoint Research. "I think they sold too many tickets." "Everyone is here. A lot of the top 100 crypto names are here. The developers are here," said Moas, who predicts bitcoin will triple to $28,000 by the end of 2019. He said he paid $2,999 for his ticket.

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