Sterling is refusing to pen a new deal offered and could be sold at the end of the season.
Parry told talkSPORT: "It's never an easy situation but, at the end of the day, as a club, it comes to the point where you have got to come up with what you think is a realistic value.
"You give the player the option [of a new deal] and you hope that he stays but, if he doesn't, no player is bigger than the club.
"Life moves on. We've lost our fair share. In my day we saw Steve McManaman go on a Bosman and we lost Michael Owen but the club picked itself up and got on with it."