Well they might be, a lot depends on how long they last, cost of replacement plates, etc. Bleach is at least predictable, once you know your demand and the local market cost, you can calculate expenses at a fairly accurate rate of a few dollars per week, but with an SWG you have that several hundred dollar initial expense for equipment, plus the cost of what may be several hundreds if not thousands of pounds of salt (and all the hauling dumping and stiring that is involved), then you get to wait for something to break, and hope it happens under warranty, if not under warranty at least hope repair parts are still available.
Ike