First of, Congrats on the round!

The article provides some interesting numbers to chew on: - 150,000 users - 15,000 business (let's call them customers) - $50,000 in monthly revenue - 6 lines average per customer.

Impressive numbers to backup traction! But they also tell the story of the freemium model very well.

Sendhub website lists cheapest paid plan at $25/month/line. This means that at most, they have 2,000 paid lines (based on $50k monthly revenue) and in the neighborhood of 400 paid customers.

These are still very good numbers and nothing to frown upon, but if you compare that to the massive adoption of the free accounts (150k users), it's very telling of how difficult it is to convert people from free to paid.