I think it is more undergrads than grads that pay money, but I think that depends on the field.
For a physics PhD for instance at Cornell you usually get paid to teach your first two years and if all goes right do your actual research on a grant. In my case the prof had written a grant for the work I wanted to do which didn't get funded, I spent a summer thinking about the problem which helped us come back with a great grant proposal that got funded.
I know Masters of Engineering students pay their own way, maybe other departments are different. I remember there being a lot of Chinese graduate students 25 years ago but now I see lots of undergrads.
For a physics PhD for instance at Cornell you usually get paid to teach your first two years and if all goes right do your actual research on a grant. In my case the prof had written a grant for the work I wanted to do which didn't get funded, I spent a summer thinking about the problem which helped us come back with a great grant proposal that got funded.
I know Masters of Engineering students pay their own way, maybe other departments are different. I remember there being a lot of Chinese graduate students 25 years ago but now I see lots of undergrads.