Hello Roy - the cost is readily available on the NHICC website - (nothing to hide)http://www.nationalhomeinspector.org/2012%20Fees.pdf
The initial fee can range between $425 to $650 depending on the inspectors background or certifications.
After the first year the maintenance and renewal fee is $150 + tax per year. Or an average of $400 for 2 years or as an example $250 per year average over a 5 year span. It gets less as time continues.
Regarding arm’s length - the NHICC has an advisory board and public members. We also hold membership with 3rd party accreditation. Bottom line - accountability beyond the internal governance.
On your question regarding training - I suggest that you are likely not fully aware of the contractual agreements between ISS and the college. So the college kept track of the actual numbers. My best guess would be in the range 50 -60%, seeing that it’s difficult for anyone to accurately track those statistics after a person even successfully completed their formal home inspection college training.