Coem to Cleveland. We've had our Sonny's unit for 5 years. We include it with every wash, so it has about 450,000 applications and is still going strong. We use just uner 2 ounces per vehicle and our cost per vehicle is 18 cents using Ecolab's Black Diamond. We use that instead of other products because it covers well and the tires stay shinier, longer than anything else we've found. We can get by with that little usage because it goes on every single vehicle and the pads never have an opportunity to dry out. Yes, the pads are expensive, however, I believe that they not only cover well but are the most economical from a chemical standpoint and with evey 4th drum you get a "free" set of pads.
Although we don't have anything to compare it to, we (and our customers) are quite happy with the end product - a shiny wheel that puts an exclamation point on every car we wash and acts like a rolling advertisement for us.