The free ones, I heard someone did great using the Tony & Chelsea Northrup course on YouTube, passed with around 85-90% and didn't have to spend another penny. Yeah I'm cheap .....er I mean thrifty.
You have to pay for the test itself plus anything else you incur. Pass it with your own ability to understand... I've also heard similar where many have passed without any sort of course...
It's time for me to retest for the next 2 years. I'll just need head back to Remotepilot101 site and just complete the Recurrent course section to prepare.