actually if you still have the warranty paper, it states limited lifetime warrany on certain parts and the electrical at 5 yrs total/another 5yrs prorated for a total of 10 yrs on electrical. You're past the 10 years for electrical. Doe's the $600 include a rebed/ cleanout of the neutralizer tank? What is the warranty on the "new head" ? Have you ever had the neutralizer rebed? The media in the tank may last 2 years, before it needs replaced, and the warranty does not include normal maintainance (sp) . So what I see is since the initial cost , you have had no problems. After 12 years its going to cost $600/ 12 yrs , $50 per year for good water.
Your help is that you could bypass the neutralizer and unplug it, since it probably hasn't been neutralizing for many years.