Slack expects some big revenue this year by Leena Rao @FortuneMagazine July 14, 2015, 3:14 PM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons Workplace messaging app Slack, recently valued $2.8 billion, expects to bring in $30 million in revenue this year. CEO and co-founder Stewart Butterfield said at Fortune Brainstorm Tech in Aspen that the company saw 100% growth in paid subscriptions over the past year. The company has 1.1 million users. Butterfield said that he’s not worried about returning money to investors. “The money is very cheap and free. I have a bunch of things to worry about, but I don’t worry about returning money to VCs,” Butterfield said. Slack has raised $320 million in venture capital, and still has $300 million in the bank, he added. On acquisitions, Butterfield said that it’s unlikely he would sell to a bigger company but “never say never.” He also said that he has no plans to add advertising to his service this year. Ryan Smith, CEO and co-founder of corporate survey company Qualtrics, has a different view. “Money is not free. Everyone is congratulating me about raising funding, and it’s the equivalent of congratulating me on taking a mortgage on a house. I wish they would say wish me luck, because it’s not free,” he explained.