My dealer wants $600 to replace my spare 2015 fob ....anyone have experience with less expensive alternatives ?

 

To make a new remote/key work - requires a software download using the factory service program VIDA to tell the car to accept the signals from the new remote. Both the remote functions and the immobilizer function (where the car will start even without a battery in the remote) A new emergency key is inside the remote also. Some have purchased ebay remotes - then found out (some) dealers will not attempt to "program" your car to your aftermarket remote. Also the emergency key needs a special machine to cut it - you may find there are no locksmiths in your area that can copy your key. When you order a replacement emergency key from Volvo - it will come precut.

Unfortunately keys are expensive for just about any high end car today -

You might ask other dealers in your area - prices may vary and sometimes the person giving you the quote may be speaking from memory, and perhaps quoting a price for a more expensive remote - like for a 2014 xc90 switchblade style.