Galatasaray doesn't want to pay over 20 million euros for Ederson while Manchester City is expecting an amount around there. I understand though considering he is already 32 years old.
I would say 32 year old goalkeeper, no matter how great, doesn't usually worth 20 million. I mean PSG wants 50 million for Donnaruma, and he is only 26 years old and could be possibly the best goalkeeper in the world right now. That is why it's clear that we are going to see City accepting lower offer eventually, if they do want to get rid of Ederson of course, if not, then they can just keep him.
No team will be willing to pay 20 million, and Galatasaray already stated they are willing to pay 10 million, maybe could go a bit higher with bonuses and such. So if they really want to make sure Ederson leaves, they should take that offer and shouldn't be that bad, it will definitely be benefit of them and not that bad.