I was a Sybase point person for years at a fortune 50 medical devices enterprise company (we had revenues of well over $1B annually on devices running Sybase dbs). There were dozens of bugs/issues I found that I pushed up the chain to an engineer and had special patches turned around within 48 hours, sometimes even hours.
Before I left that job I started playing around with Rails and mentioned MySQL and Postgres for a potential greenfield project. I was told it would be fine for internal use but no way, no how were they going to deploy any software without that kind of parachute based on economic leverage.
Often enough you'll even get similar turn-around times from the community, if you can't (or don't want to) afford such a support contract.
Making software work at scale without that economic leverage could never work in theory. It only works in practice.
Oh, and those who did it were above oracle in terms of data size making it rational decision too. The calculation is still different for majority of companies.