Subway is actually cheaper than what you'd pay to buy all of the ingredients from a supermarket. The only way you'd even come close is if you buy in bulk eat subs everyday for several weeks so the ingredients don't spoil.
You missed the point though - there are other sub shops that DO buy in bulk, sell subs cheaper than Subway, make a profit, AND use better quality ingredients & more meat/cheese in the subs.
Despite that, if you were making subs for a family of 4, I think you could have more meat on your subs than you would get from a subway sub, better quality meat, and could do it cheaper. "Bulk" not required, unless you consider a single head of lettuce to be "bulk."