As I know, around 2million people is on the Hajj every year. There are around 1.5billion Muslims on the world. Half of them are male, which is 750million. If they live 70 years long, then 140million Muslims can visit the Hajj. Thus, around a fifth of Muslim men do the Hajj in their life.
However, the plane tickets are far cheaper outside of Dhul'Hijjah (as far I know, particularly the planes coming back after transferring pilgrims are very cheap).
Thus, would doing the Hajj outside of Dhul'Hijjah be better than doing nothing, or not?