I'm not sure he has? It's a job and he hires an agent to get him the best deal. If, I dunno, Funes Mori did the same thing, nobody would bat an eyelid - where Ross was born shouldn't make a difference.
I'm an Everton fan, but if the club asked me to pay 50% more for a season ticket to prove how much of a "boss blue" I am, I'd tell them to do one. Same with Barkley - why shouldn't he maximise his compensation for his services at the club?
There's no chance he's getting a better wage at another club.
He gets the wage, and treatment he does at Everton because of where he was born.