First up, what is the Serial Number of the machine..? If you don't want to post the full S/N here then PM it to me.
Depending on how the machine is currently configured you may need any or all of the following: -
1. Additional section(s) installed into the main control valve for the auxiliary function. I can see 2 possibilities, one priced at $6000, the other at $4200.
2. 2 x Floor-mounted pilot valves (pedals) to control the auxiliary function for the thumb.
3. Pilot hydraulic lines from the cab to the new section in the main control valve for the auxiliary function.
4. High-pressure hydraulic lines from control valve to base of boom.
5. High-pressure hydraulic lines from base of boom to end of stick.
I can easily see how that lot could potentially add up to $12,000 complete, but a lot depends on how your particular machine is configured right now. If you are lucky enough to have a main control valve that already has a suitable section in it to run aux hydraulics it could cut the cost in half.