AFAA offers the Primary Group Exercise Instructor certification for $99.00 twice per year called APEX. www.afaa.com
Stick to organization such as AFAA, ACE and ACSM
Cheap is cheap.
Perhaps it might be a better approach to look at the return on your investment as far as investing in your career is concerned.
It doesn’t always mean that something that is expensive is a quality product. I have spent good money on workshops run by reputable organizations in this industry only to be disappointed.
Do your research. Make sure your motivation for choosing the credential is bigger than:
1. Everybody else has it.
2. I can afford it.
Lastly, in the end when you have earned your credential, you should feel that it is something you worked for and that was instrumental in helping you to grow professionally.