You might be interested in our Unity Tokens micro-transaction API. It's free for Unity developers and designed to run seemlessly in your game. You can download the API and read the easy setup tutorial here:
Unity Tokens API and Getting Started Tutorial
All of the program details are on our site, but we currently offer a 70% split to all developers using Unity Tokens. Our current exchange rate is 800UT : $1 USD. We currently issue bi-weekly payouts to accounts via paypal and soon via bank check and direct deposit.
We also offer helpful micro-transaction tutorials to help you better understand how you can design a virtual economy in your game.
Unity Tokens microtransaction Design Theory
If you have any questions about our program we will do our best to answer them.
Unitytokens.com