An improvised message tells passersby to "buy bitcoin" on the University of Oregon campus in December 2017 — the same month the cryptocurrency's price rocketed from $10,000 to nearly $20,000.

An upcoming conference dedicated to cryptocurrencies and blockchain technology has stopped accepting ticket payments in bitcoin, suggesting that the method was slow, costly and labor-intensive.

The North American Bitcoin Conference, held in Miami next week, said on its website that network congestion and manual processing influenced the decision to stop accepting payments in cryptocurrencies.

Last minute tickets were selling for $1,000.

"We have, and always will, accept cryptocurrencies for our conferences, up to fourteen days before the event," the organizers wrote. "However, due to the manual inputting of data in our ticketing platforms when paid in cryptocurrencies, we decided to shut down bitcoin payments for last minute sales due to print deadlines."

CNBC has reached out to the organizers for further comment.

The conference organizer, Moe Levin, earlier told Bitcoin.com that his company was working to get bitcoin cash or other digital assets with cheaper fees integrated into the ticketing system. He told the news site: "We wish this was easier, but no ticketing options exist which can handle large volumes of ticket sales, and transaction fees on the Bitcoin blockchain exceed $30 at certain times of the day."

Relatively slow transaction times and high processing fees for bitcoin payments have led to many merchants rethinking their decisions to accept cryptocurrencies. For example, tech giant Microsoft temporarily stopped taking bitcoin as a payment option at its store, before resuming such transactions. Last month, gaming platform Steam also stopped accepting payments in bitcoin, citing "high fees" and "volatility."

According to industry site BitInfoCharts, in the last three months, the average bitcoin transaction fee was as high as $55. On Jan. 9, data showed the fee was about $31.

Bitcoin's relatively high transaction fees are, however, profitable for so-called bitcoin "miners," who work out complex cryptographic puzzles to add transactions to the blockchain — a decentralized record of all bitcoin transactions. In return, they are rewarded bitcoin.

Meanwhile, data from Blockchain.info showed that, at the time of publishing, it takes an average of 51 minutes to confirm a bitcoin transaction. Over a 30-day period, that average time was as high as 3,564 minutes (more than 59 hours) on Jan. 1.

Bitcoin traded at $14,466.97 per token as of 10:31 a.m. HK/SIN, according to data from CoinDesk.