As a service provider in the electronic security industry with much experience in the strata environment, I'd be more than happy to provide you with some site specific recommendations and an estimate of costs associated. In addition to the access control and intercom requirements, we are also able to perform any additional work that may be required to facilitate the desired outcome. (In older buildings, the front door, frame and adjacent window/s are often replaced as part of the “security building upgrade” if they are past their prime. For a door to automatically close and lock reliably, the door needs to close unimpeded every time).
Wireless intercom solutions were mentioned, but my advice would be to stay with a hard wired system for reliability and serviceability. Although a wireless system may have a lower installation cost, the actual equipment will be much more expensive than wired, and the technology is far from perfect.
In terms of price, I think you'll find that it's not all that bad, particularly with fifteen owners to share the cost. It's much more of a hurdle when there are only three or four units in a block.
Another way of achieving greater value for money is to incorporate other work into the same project. If we're going to be running a cable to every unit anyway, then the cost to pull an extra cable in for NBN connectivity, a CCTV system or pay TV is a small addition now, but will save tens of thousands of dollars compared to separate projects.