I think 15 to 20% commission is fairly usual for most strata managers (and contributes to their management fees). Legally, any commission should be declared, and declaration details included in the contract.
If it IS included in the contract, I’m not sure you can legally get your insurance elsewhere, if you’ve signed a contract that includes your strata manager as your broker. (Maybe someone else can advise on this). Also if you get your own insurance then you have to consider how you’d pay your strata manager for assisting with any claims and communication with the insurer.
If your contract is due for renewal you could try negotiating with your strata manager about the commission and or about what is included and not included in standard services.
Some Strata Managers don’t charge a commission (their other fees may be higher though), and some offer a range of management option packages that include ones where you obtain your own insurance.
Check your contract. If it doesn’t include agreement that the strata manager will obtain insurance, you could get your insurance elsewhere. You’ll need building details and claims history.
We saved about 17% off our premium this year by going through Strata Fair insurance broker, who were recommended by the Owners Corporation Network. To be double sure, we voted on it at an EGM and formally authorised with a letter signed by committee officers, for the new broker to act as sole broker on our behalf. They were then able to obtain all necessary info on our behalf.