According to the fairly silly Being Batman:
But you don’t have to be a billionaire to become a caped crusader. Using commercially available training, technology and domestic help, the average guy could conceivably equip himself to become a real-world superhero, provided he’s got at least a couple million to spare.
The bottom line:
Final Cost: $3,365,449The Training: $30,000
The Suit: $1,585
The Belt: $290
The Car: $2,000,000
The Cave: $24,000
The Alter Ego: $1,109,574
The Butler: $200,000