Its not any more expensive. With the cost of meat now, its actually cheaper to eat avocados and beans than it is to eat a hamburger.
If this is something you really believe in, then you'll succeed. Its like kicking any other habit, just give yourself 3 weeks to change your "urge" and you'll be fine
Not that I don't crave the occasional cheesesteak, but when I really think about biting into that "meal of death" the craving quickly passes