Additionally, they had the opportunity to capitalize on Campfire in a way that they could have closed the market for realtime collaboration before Slack. Obviously Slack is a superior product (and given 37signals opinionated product philosophy I don't think they would have ever built something so comprehensive) but still... they had a 7 year head start on Slack. A lot of orgs used Campfire every day, and probably plenty still do.

But I appreciate their commitment to focusing on one thing.

Basecamp's revenue and efficiency is of course impressive, but I'm not sure a multiple like Atlassian's would apply. Investors could reasonably assume (or know, if they're privy to their plans) that Atlassian is planning to use those 1100 employees to go after a number of markets, whereas Basecamp has shown their preference for focus and managed growth.