It really depends on the software in question. I work on DBMS. The cost of doing it yourself is potentially much higher than your comment indicates: * Time-to-

It really depends on the software in question. I work on DBMS. The cost of doing it yourself is potentially much higher than your comment indicates: * Time-to-market -- Rework due to mistakes when implementing or deploying applications * Risk -- Fixing problems may take [much] longer than for supported software * Resources -- Extra personnel to do software support and maintenance. This gets a lot more painful once software is long in the tooth and no longer cool to work on. None of these have anything to do with OSS in particular. And for many people the costs are outweighed by benefits like understanding the technology stack and not being in thrall to costs they can't control. In a similar vein I used to fix cars myself. I now take them to the mechanic even though for many problems I could do a better job albeit at a high cost of time, parts, and tools. It's cheaper to focus on work that I'm good at. I still miss car mechanics though.