This is what I found. I said one-time event coverage was $40, it's $25, $40 are the annual club dues.

"The annual fee to charter a club is $40. After it is chartered, your club will receive a certificate as proof of its chartered status with AMA.
The club charter year starts on March 31. This runs concurrently with the dates of the liability insurance coverage, which is provided at no
extra cost as a benefit to the club and the club officers."

"Flying Site Owner Insurance Coverage: Most property owners want to be assured that they are protected if they allow a chartered club to use
their property as a flying site, so they will ask for an insurance certificate that will name the property owner as an “additional insured.” This coverage
safeguards the owner if he or she is named in a claim because of an accident caused by an AMA member and/or club. Clubs can obtain this coverage
for the charter year or for specific event dates. There is a processing fee of $80/certificate for the charter year coverage or $25/certificate for specific
event coverage. Please complete this form and submit along with the appropriate payment.
The coverage provides up to $2,500,000 of primary liability insurance coverage to the flying site owner."

It is incredibly cheap. There is no way a club could find coverage like this on their own.