Why are data charges so high?

I think it is crazy that you could be charged $1 per MB of data over wireless.  In Australia, if you're not careful in choosing your provider, you could be in for a very nasty surprise.  I feel sorry for SMB owners who are not that technical and sign up for these outrageous prices.

http://www.telstra.com.au/business/products/internetanddata/mobilebroadbanddataplans/mobilitypacks.htm