How much money is required to get to the key in the Fable 3 Sanctuary treasure room?

Solution 1:

I believe the number is 5 Million. But here is the thing. Once you have that much the chest will be covered in gold and inaccessible.

To get rid of it all you have to give your money to the royal treasury which you can do if you are the king. If you aren't there yet keep playing.

Solution 2:

The number is exactly 5 million. The key will appear to disappear when you reach this amount, but it is not treated as a regular gold key you can pick up and store. When the key has disappeared, this means you can successfully open the chest if you get rid of all of your money.

You don't have to get rid of all of it to access the chest, but I think anything over 100,000 in your personal stash renders it unobtainable.