The change in people is amazing. That said your estimate is not far off for cost of just the implantable generators, plus the leads. Add on cost of surgery and doctors bills and hospital stays and your probably under estimating.
Not to mention typically it’s the last choice for pain treatment, so it’s a the end of typically years of pain. Also it only lasts for about a dacade due to the battery so you will need to repeat the surgery and buy a new device periodically.