Being a high draft pick and showing glimpses of brilliance isnt enough for that kind of money. You'd at least want a player who has strung a good, full season together.
Sydney pay 300k + each for both Kennedy and McGlynn which was overs at the time, look how that played out..... sometimes its overs that gets the job done. Id be happy to give Mitchell 400k, 2 yr deal, re-evaluate after that and adjust accordingly.