Of course it wouldn't. Because players peak and mature at vastly different rates.
You don't measure every player by their age because their ability, aptitude and capability to make it at a particular level or club will always vary significantly.
Sterling has served his apprenticeship at Liverpool, and now he's making a step up to play under greater pressure, under more scrutiny, among some of the best players in Europe competing for honours at the top of the domestic game and in Europe.
He's shown ambition. Time will tell if he develops into the player he truly has the potential of becoming, and if he does, £49m will be small change.