I think for Enterprise you should include professional services and consulting in TCO. And usually the Enterprise SaaS tools you mention are a bit cheaper on licenses, but very expensive on the consulting. It makes sense because if a tool is open source and known there is a lot more talent in the job market, if a tool is closed source it takes money just to learn it and people have to recover that investment.

But you are right, I think Dittofeed should sell their benefits to C-Suite execs, not to developers.