The pricing information is public and well known. The ACE system sells for $1500 when added separately though can be found discounted to $1300 at
American Sale. When done as an option to an existing spa, the ACE system may be discounted further (as you know, dealer prices are discretionary). As for the replacement cell,
this post at the beginning of the year quoted $845 which is consistent with what you heard.
It's a premium system with premium pricing. You can think of the system as a combination chlorine generator and ozonator because the boron-doped diamond electrodes do just that -- they generate chlorine from the chloride in salt and they generate hydroxyl radicals from water. An ozonator generates ozone, but when ozone breaks down it produces hydroxyl radicals. The idea is to oxidize bather waste before chlorine has a chance to react with it and that minimizes chlorinated disinfection by-products. The residual of chlorine left in the spa is the bulk-water disinfectant.
It is interesting that the manual for the system makes no mention of using Cyanuric Acid (CYA) aka stabilizer or conditioner. Without CYA in the water, the recommended chlorine target minimum of 3 ppm (maximum of 5 ppm) will be harsh on swimsuits, skin and hair and will outgas chlorine faster to degrade hot tub covers. By using 30-40 ppm CYA in the water, this effect can be significantly lessened by a factor of roughly 8 to 30, depending on temperature. I suppose this isn't that surprising since the chlorine/CYA relationship is something not well understood in the pool/spa industry except that CYA protects chlorine breakdown from sunlight. CYA's significant moderating effect on the active chlorine level isn't brought up except in a negative way when the CYA level is too high.
