Every once in a while, I begin typing a search in Google and I can't help but laugh what the most popular searches are that start with the same words I'm using. I'm sure you've seen this before. I was looking up the cost of a part to repair my car and came across this:
The first one is the best. How much does it cost to be batman? Ha! This implies that more people are searching for how much it costs to be batman than are searching for how much is costs to have a baby, mail a letter, build a house, and get a passport. (And more people are wondering about Batman than Iron Man.)
So I had to look this up. Apparently, a rough estimate is something to the tune of $682,451,350. But if you're Bruce Wayne, whose wealth is fictionally estimated to be around $6.9 Billion, then you've got a few hundred million to throw around. :)
Try starting to type some things in Google and see what suggestions you come up with. Let me know if you've got any good ones!