All potential bonuses

Can anyone confirm that the higher the level of the equipment, the sooner it becomes epic and then unique? I hear people saying that, for example, a spectrum goggle would become unique/epic quicker than broken glasses, even though they are in the same level range.

I've had a friend cube his HTP over 80 times and it's still rare.

I think since people end up cubing higher leveled items by default, people will most likely draw those conclusions.