This document compares the total cost of ownership of open source business intelligence (BI) tools to traditional vendor BI tools. It finds that open source BI tools can save between 50-15 times the cost of traditional vendors, depending on the size of deployment. Savings increase with larger deployments as the per-user cost of open source BI decreases while traditional vendors' costs increase. For a small deployment of 25 users, the average per-user savings is around $1,500 over 3 years, while for a large deployment of 500 users the savings is around $3,000 per user over 3 years. The cost differences stem from the pricing models of open source being simpler with per-user costs that decrease with scale, unlike traditional vendors