Dumfries can be signed for 25 million euros...
I think it is a quite good opportunity for teams looking for a solid RB.

He is 29 so there could be different opinions on the fee comparing to this info.
It is definitely a good opportunity, and i am pretty sure quite a lot of teams around Europe would be assessing the situation right now. City is one big team that desperately needs a right back, Kyle Walker is leaving, and Matheus Nunes has been playing at right back since last season even though he is a midfielder.
That said, i heard City were interested in Livramento from Newcastle, but there is no progress as regards that, and it would cost City a lot of money. Activating Dumfries' release clase seems like a better option IMO, that's if the player is ready to leave Inter and join City.