So in practice money is effectively being donated (donating hw is not free) to be spent on CI, not very differently than in our case, but you're delighted to not know the numbers and like to imagine it's $0. Ok :^)
That's true but I'm pretty sure that the goal is to have a large number of individual sponsors. A handful of large corporate sponsors can later try to use their sponsorship to exert unwanted influence over the project.