funding thumb3 Bill.com bags $8.5 Million to make bill payments better and faster

Bill.com that helps streamline businesses’ payment modes closed its current round of funding at $8.5 Million. The round was led by August Capital along with participation from existing investors DCM and Emergence Capital. The firm removes the complexities that surface due to the involvement of paper work in transaction and bill payment. It charges $24.99 per user per month and $9.99 for each additional user. This does save time but how it manages to keep their costs low is something I fail to understand. Anyone out there with an explanation?