The hype over the chat app Clubhouse has reached inside China’s walled internet garden, where an invitation to use the service is being sold for $20 online.

The invite-only app, which allows users to post voice messages in chat rooms, saw a spike in interest in the country this week after billionaire entrepreneur Elon Musk joined a session on Tuesday.

For the same reason that long lines at a restaurant get attention, Clubhouse has attracted a growing number of Chinese users interested in tech and media.

On Idle Fish, an online second-hand marketplace owned by Alibaba, people are selling Clubhouse invites at prices ranging from 150 to 300 Chinese yuan ($23 to $46) each.

“Very fun! Try new things! The hot app in Silicon Valley,” wrote a seller in Beijing, who was peddling an invitation at 180 yuan ($28). “You can have a glimpse at the networks of big-names and influencers.”

Another seller in Shenzhen is selling invitations at 220 yuan ($34) each.

“No more left if you are too slow,” the person wrote. “Listen to Musk and Robinhood CEO truthfully recounting the GameStop saga. Listen to product managers at Alibaba and Meituan debating each other.”

Clubhouseinvitation briefly became a trending topic on the microblogging site Weibo on Tuesday. Users have also posted screenshots of their Clubhouse profiles to seek followers.

But an invite is not enough to join the club. As the app is not available in mainland China, users of the service must change the location setting of their Apple App Store to overseas. They will also need an iPhone or an iPad because the app is iOS-only right now.

China has blocked most international social apps, including Facebook, Twitter, and even Tinder. Only services that comply with China’s censorship rules, such as LinkedIn, have been allowed to operate in the country.

So far, there’s no sign China’s censors have come for Clubhouse, meaning the small number of Chinese users can discuss political topics freely in the chatrooms.

“The internet police has yet to secure an invitation,” a Weibo user commented. That could change at any moment.

Follow Viola Zhou on Twitter.