Slack, a chat app for businesses, announced today that it now has 1.1 million daily active users, with 300,000 of them paying for premium features, such as unlimited chat history and third-party integrations.

This milestone comes two months after Slack raised $160 million in a round that more than doubled its valuation, to $2.8 billion. Slack’s story has been one of remarkable growth, especially in the enterprise world. In February, a year after it publicly launched its namesake chat platform, the company had 500,000 daily active users and $12 million in annual recurring revenue. The startup says it now has $25 million in such revenue.

What’s particularly fascinating is how the valuation breaks down per user. For Slack, each user is worth about $2,500—by far the highest among select tech companies in the chart below. At $282 per user, LinkedIn comes in second with almost a magnitude of order difference, based on its 97 million unique users. That the two sit at the top points to the high value placed on business users.

Some notes on our methodology: For public companies, we used their market capitalization as of US markets close yesterday, June 23, and the monthly user figures from their most recent earnings reports. For private companies, we relied on what companies have publicly said, and if that was outdated or not available, we used recent news reports for valuation and user numbers. The data for WhatsApp, Instagram, and Twitch were as of their acquisition announcements. They were included to give an idea of what Facebook (WhatsApp and Instagram) and Amazon (Twitch) paid for the startups on a per-user basis.

The chart above is a good reminder that, for all of Slack’s growth, it’s still a very young company—one that investors happen to be very bullish on. The user base is still small, but there is a lot of opportunity, especially given Slack’s giant cash pile and low marketing costs. By 2019, enterprise communication is expected to become a $23 billion industry, up from $13 billion in 2014.