He decided he was worth more than originally agreed to so it is on him how much he's being paid.
I take a view that a player is only worth what a club is willing to pay him. Just because he wanted $600k doesn’t mean the club has to pay that if they don’t think he is worth it, or has the potential to each that value.
They could of just let him walk, like they have with a number of players over the last 2 years.