24 quality and fast development will be 5 stars all season at your level, and 5 stars next season as well...

Next season you'd need about 2.5-2.6M to sign a player like that, so imho better get him now for 1M.

But since you don't rate 5 star talents, let me ask what level is you current talents? must be lower since you have trouble clinching CL in 4 star average league...

You make a huge mistake holding on to him, trust me. Take the 300k profit and sign a real talent instead