I agree to some degree but if you had a player in your side that was say like, Gazza then most if not all wouldn't complain as it's clear he's night and day better than everyone else (he may singlehandedly drag a sorry excuse of a football team to a Cup Final!). But this guy is not that player, he's not worth £170k pw. Jesus and Sane at City are both on £90k pw. Bernado Silva is on £120k as is Gundogan, in fact that salary would make him the 4th highest paid player at City behind only Augeuo, De Bruyne and D. Silva.
I'm not saying he's a bad player, he's just not a special player.
It's not really the madness it's made out to be tho , , if it's a 4 year deal he earns £35.3 million , even if the deal is £40 million with signing on fees agent fees etc it still represents value, Sissoko on a four year deal is probably costing us 50 million when you include his transfer fee.