Your partner should be able to help you out with architecture and prices.
You will get a 2nd virtual controller that can run on your server farm in your backup data centre. You build it and create a cluster to add both controllers to.
You don't need extra user licences.
Here's the super-fiddly bit though - you will need to change all your users and devices so that they are registered with the new controller as their secondary. You should be able to do this by importing a csv.
Your other bit of resiliency will be to get another MBG and a 2nd SIP service into the 2nd data centre. If the failure mode they are thinking of is the unavailability of the main data centre, then this 2nd SIP service should be a requirement.
Your licences for a new virtual controller and a new MBG plus a bit of SWA will only be about $2k, new SIP channels on the other hand can get really pricey. 30 will probably add up to over $4k. And then whatever labour is needed will pretty much cost that much again, depending on how much you do yourself.