Only TSMC gets a "very nice deal". Without competition every IHV will pay big money to get wafers.Since we are not talking about the same die sizes here what you are saying is irrelevant.
AMD is number ONE 7nm customer at TSMC currently with 30K wpm , im sure they got a very nice deal.
So Ampere is a big deal for the whole business. The last big non TSMC GPU from nVidia was NV40 from IBM.