Of the API's that are available through a wide variety of brokers, it looks to me as if Cunningham T4 API and Rithmic R|API are the main two API's that are very low cost to use for low-volume automated trading. It seems that Trading Technologies and CQG are too expensive for me to use in this low-end context. Is this roughly correct, or am I missing some things? I want full access to all exchange-defined and implied contracts and futures options at ICE and other exchanges. If I am right, what are some pros and cons of Rithmic API versus Cunningham T4 API (or other alternatives)? Thanks.