[outop]

The company that 'owns' Redis or Elastic also do not need to develop the software they are selling. They already have it, since its creation for free on a non-commercial basis.

Without competition, they are free to charge any rent they like for it.

If you think that the person that originally wrote Redis or Elastic should have an exclusive license to charge people to use that software, that's a totally valid opinion and a totally valid licensing/business model. However, it has nothing to do with open source software.