We have used AWS since long before Amazon was a supporter of Rust, and then they started supporting us, and I am grateful to it. Paying for Rust's infrastructure, as far as I know, is not cheap.
I am not a member of the foundation and so can't really speak to what is being spent currently. As far as I know a public budget has not been posted.
The risk is that they can set the direction to anything. They might be amazing stewards, they might spend it all on useless things. We don't yet know. I do know that many of the folks in the foundation have their hearts in the right place.
Again, the theme isn't about specific actions, it is about consolidation of control.