I remembered the device costing about $20,000 from when I did my post-bacc research (03-04), but didn't know for sure, so I found an article you can use. The article says 12,000 pounds sterling, which is about the same.
Emma McIntosh, MSc 1 *, Alastair Gray, PhD 1, Tipu Aziz, MD 2. (2003) Estimating the costs of surgical innovations: The case for subthalamic nucleus stimulation in the treatment of advanced Parkinson's disease. Movement Disorders. 18(9): 993 - 999.