https://basecamp.com/customers mentions "100,000+ companies rely on Basecamp to run their business." Since it does not mention "1,000,000+ companies", I think that "2.8 million accounts" refers to users, not companies.
Although current pricing for Basecamp 3 is $99/month (for unlimited amount of projects), previous Basecamp versions (Classic and 2) had other pricing models. Significantly cheaper when you were managing less projects, a bit more expensive for more than 100 projects, IIRC.
Basecamp / 37signals also has paying users for some other applications, e.g., Highrise (CRM, 10,000+ organizations, but closed for new signups), Campfire (instant messaging, closed for new signups), Backpack (intranet for businesses, closed for new signups). They continue to provide those services though, "until the end of the internet" :-)
So, in short... it's not as simple as 2.5 million times 99 USD.
Ignoring paid accounts for the other products, and severely underestimating the number of accounts at the 99 dollar level as 75,000, the monthly revenue could be 7.5 million dollar per month minimally, or 90 million per year. I would guess the actual number is twice that. Either way, it's impressive by any comparison.
Although current pricing for Basecamp 3 is $99/month (for unlimited amount of projects), previous Basecamp versions (Classic and 2) had other pricing models. Significantly cheaper when you were managing less projects, a bit more expensive for more than 100 projects, IIRC.
Basecamp / 37signals also has paying users for some other applications, e.g., Highrise (CRM, 10,000+ organizations, but closed for new signups), Campfire (instant messaging, closed for new signups), Backpack (intranet for businesses, closed for new signups). They continue to provide those services though, "until the end of the internet" :-)
So, in short... it's not as simple as 2.5 million times 99 USD.
Ignoring paid accounts for the other products, and severely underestimating the number of accounts at the 99 dollar level as 75,000, the monthly revenue could be 7.5 million dollar per month minimally, or 90 million per year. I would guess the actual number is twice that. Either way, it's impressive by any comparison.