You could try Bitcoin Essentially, your authors provide you with a Bitcoin address (trivial for them to acquire using any free and open source Bitcoin client ) and you keep track of whatever they have earned in your local currency as part of your business.
When the time comes to make payment you buy some bitcoins on an exchange at the current spot rate and send them to their address. This process is easily automated. They get their money within 10 minutes anywhere in world. It works for any size transaction from fractions of a cent up to millions of dollars (depending on the exchange rate and overall market capitalisation) and has extremely low transaction fees (typically less than a cent for several hundred dollars).
Run your affiliate program through one of the major affiliate networks, like Commission Junction or ShareASale. They've been handling paying international affiliates for longer than your business has existed, so let them deal with it and absolve yourself of all the many tax complications involved in making payments yourself.