R/3 is what SAP
, the third-largest software house in existance, earns their money with. It's a company-wide workflow management
system used by companies to automatize and integrate all of their business processes - customer relationships, supply chains, accounting, everything.
R/3 has about six million lines of code
, and a big installation costs a couple of hundred thousand dollars. On top of that, you need to hire expensive specialists to customize the system for your particular needs.
Obviously, the benefits outweigh the costs, if you consider that the system is used by more than 13.000 customers, including more than half of the top 500 largest companies. Microsoft manages their own business with R/3.