Still doesn't really make sense. Southampton gave him a chance. If we didn't pay that for him he'd still be playing first team football at Southampton.
We'd don't have foreign stars because English players are expensive. It's often because they're just better, offer something else, or are just good players in their own right.
Will Hughes (for example) being cheaper may make a top club more willing to buy him, but it wont do anything to guarantee him a 'chance'.
And United paying £27 million for Shaw doesn't do anything to stop West Ham or West Brom giving youngsters a chance, does it?