That's bullshit. A more accurate statement would be that large companies have a lot of momentum and often have the turning radius of an aircraft carrier, but that have absolutely nothing to do with technology choices. The age of "no one got fired for choosing IBM" is over.

At my company, the team using Java+PostgreSQL is twice the size (~120 people) of the team using C#/MSSQL (~60), and the only ones really "stuck" right now re: tech are the ERP folks, because that has such a huge switching cost in the change management/training side of things, not to mention the whole "what do I do with all my legacy data when it doesn't have a natural fit in my new ERP?" problem.

IME, large firms (including government agencies) don't like not having a support contract in place for key infrastructure.

They don't seem to mind open source as such, and will use open source without support contracts for tools that aren't key infrastructure (or for libraries for internally-developed software), and probably wouldn't mind open source with a support contract for key infrastructure (but for a lot of things, proprietary s/w vendors are just better at selling support than the people selling support for open source software.)

Large (tech) company employee here. For the project I work on, most of our production stack is made out of FOSS software that's wrapped up in support contracts.

At these prices it seems like you could take Postgres, wrap it in a support contract, and call it EnterpriSQL and still charge less than MS.

Not my experience.

Government dislikes open source (you know, communists).