I don't think City will pay the release clause. City will want to deal at around £80m which in my opinion it means the deal won't get done.
With regards to Neves, I think Benfica can be brought down from the buyout clause. £80m for them is very different than what it would be for Newcastle. Even with PSR and FFP, Newcastle will want to offload others to make up the numbers before they have to be forced into selling Isak, Bruno and Gordon.
Also,he is a Jorge Mendes player and Txiki has good relations with him. It's an "easier" deal.
Also Bruno will be demanding £250-£300k a week, Neves will be on around £100-150k. The overall package is smaller. This is an important factor many of us forget to include. We just judge the transfer on the transfer fee.