Insurance Commission what is standard?

Our Owners Coporation is currently exploring changing our manager and we requrested some proposals from suitable managers. I noted in one contract that the Body Coporate Manager receives 15% commission for insurance and if the insurance the Owners Corporation chooses does not provide 15% commission to the manager, the Owners Corporation has to pay the Manger the difference. I was very surprised indeed to see such a clause and would like to find out if this is legal, if it is, it appears to me to be morally wrong. Happy to pay a fee for a service but getting three insurance quotes is not worth this amount. Given Insurance costs are one of the highest expenses of our owners corporation, 15% of our insurnace is a signficant amount.