1. Run a program that will generate a wordlist, put the output in an queue.
   
2. Have a bunch of EC2 instances that take input from the queue and generate MD5, SHA1, etc hashes from the queue. Store hash to password mappings in SimpleDB
   
3. Depending on how fast inserts into SimpleDB are, it might make sense to store the hash/password mappings on disk or in S3 and stream them into SimpleDB
   
4. ???
   
5. Profit!
   

Since the Amazon AWS services have set prices, it should be pretty easy to calculate the dollar cost per n passwords. I'm guessing that number would be pretty low.

See also: http://twitter.com/jf/statuses/536491112