I'd give Sanchez+30m for Martial. Confident Wenger can develop him into a world class talent. It'll be best for all parties involved, if Sanchez moves to Utd then that kills martials game time.
I dont think there's much wrong with this post, the guy is talking about it from an Arsenal perspective.
The first bit - he'd give Sanchez plus £30m for Martial. Good shout, he is only recognising what a talent Martial is.
Confident Wenger can develop him. Why not? Wenger has done well developing young players, and there is the French connection.
Sanchez arriving could limit Martial's opportunities. This is a (small) concern. Sanchez likes to start on the left hand side, so they will be competing for the same position to some extent. (Of course Mourinho will also look for ways to play them together.)
The only bit I disagree with is that it would be best for all parties. It would be great for Arsenal. It may well be quite good for Martial as well - he would definitely, definitely play more, for a manager more inclined to trust young players. The party it wouldnt be better for is Manchester United. So almost certainly wont happen. Still, you can see why an Arsenal fan would hope.