This is how you get the 'Richest Man in Gotham' achievement in Lego Batman for the XBox 360.

Details: Max out the stud counter.

This one will seem daunting at first, but it's quite simple once you get some of the extras.
First, make sure you find all the power bricks in each area of Chapter 1-Villain. They aren't hard to find.
Next, you need to purchase them.
They are the score multipliers. You'll need 15 million studs to buy all five.
Once you have them, turn them all on for a max of 3840x your total accumulation. Once you have them, head to any area where you still need minikits.
The 50K stud bonus for finding all 10 will be affected by the multiplier, giving you near 200 million upon completion.
Keep collecting and when you finally hit 4 billion studs, you will be the richest man in Gotham!

Enjoy!