Every organization worth anything insists on yoga instructors participating in continuing education. This prevents student injuries and makes you a better yoga instructor. Most of them charge an arm and a leg (thousands). After you successfully passing your yoga teacher training course, aura wellness center sends you a yoga teacher diploma that's good for two years.
After the two years you send in your independent research that comes free with the course or proof of attendence at any yoga teacher conference, workshop, or take an online course for yoga teachers from aura.
The cost for the re-certification with aura is $95 for 5 years. That's the lowest price I've ever heard of anywhere and really they just want to make sure you're active in your studies, which all of us do any way.