Let us be straightforward with ourselves and tell the truth, Asernal as a clubs doesn't have to sell off any player with the hope of getting a better offer, knowing very well how Asernal performance in the last concluded season went, at least their performed near excellent so what the need to scatter the already formed team, for me injury and age are not really a basis to sell an old good player.
Which players need to be sold, and why? Considering their performances last season, they were much better. The most important thing Arteta needs to do is build the players' confidence so they develop a winning mentality. There's a lot of hope for this squad now, as bringing in a number of quality players will significantly increase Arsenal's chances of winning the Premier League. I agree with you, as there's no need to sell some of Arsenal's players, as Arteta's core players have generally performed quite well in the previous two or three seasons.