Security Keys and Fobs

We have recently purchased a 3 Bedroom Apartment in a Block were we have another Apartment. We require Bi-Lock Security Keys. We received two at the Time of Purchase and have additional Tenants moving in. We have been disputing with the Strata Manager who wants to charge us $122.00 for a Key we can but from the Local Locksmith for $21.50. He Claims the additional $100.00 is a refundable Deposit, But, since these Keys are required for individual Tenants, and since the Residential Tenancy Act requires us to provide a Key for each Tenant, we say that the Key will never be returned for a refund of the “Deposit”, so we should not be expected to pay this $100.00 Rip Off. Should we take this Matter to NCAT, or is there a Strata Management Ombudsman?