The thing you have to evaluate is after you have spent your tokens on the player, then used green packs to power train him (and red packs for injuries), while possibly using more tokens to buy packs, add on the time it takes to train him (as you say you tanked a season too - so you could discount one of those stars if you hadn't) - then compare it to what you could get from a scout the question is - is it really that great?

I've never used an academy player. Maybe this is due in part to the fact that I already have several far superior players in the team to not make it worth while.