They are entirely different. A studio making changes and merging those changes into master is equivalent to an individual making changes by themselves, for free, then merging those changes into master. Here, people are paying for the promise that these changes will be merged into master (among other things). If the public was paying the studio to do the work under the assumption those changes will end up in Blender, then they would be similar, and that would be a similarly bad idea.
No one here is debating whether developers should get paid. If you would like to understand my reasoning for my view on this and why it isn’t a good idea, feel free to head over and take a read.